CHASSIS – BEST PRACTICES
Contents
1. EXTENDING WHEELBASE MOVING V A SEHR ER assa nee ane 1 Pr ean M 1 PN S este TUN ERN 1 1 Altering the mm 2 Frame Splice 2 Frame Splice Preparato o om 3 Frame Splice Procedure erse E AEEA Ea uA ET AREFE ES SES PANEON EEEE 4 Extending the Frame Rear OVE rani E cT 7 gio che M 8 SS I SIUM TNR TE TET 9 Analyzing Frame Failure Causes c C 10 Mel C E EE E E E E A 10 Excessive Bending MOMEN 10 Stress e n rS E VEERSE NE APENE SEAN AAEE E NoE E eVa nni EEE Eie 10 Attaching Reinforcement Sa sssini anaa ASO AAKA 12 Terminating TUNE 13 Frame Repair and Reinforceme2. continued on next page UPPE INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Welding Methods Four basic welding types Figure 14 are used to repair and reinforce frame rails These methods can be used with any type of material TRANSVERSE BUTT GROUND LONGITUDINAL BUTT OR FILLET MACHINE WELD MANUAL WELO TRANSVERSE FILLET LONGITUDINAL FILLET SKIP Figure 14 Continuous Fillet Longitudinal Butt Weld This is used to weld a continuous bead along a reinforcement on the frame rail web section or to add gussets or plates to crossmembers Continuous fillet welds should never be made across frame flanges or along their inside edges When welding in a flat position use high range of electrode current For welding overhead or in difficult areas use low range of electrode current Use the voltage specified for the electrode Groove Welding This basic repair weld is also called transverse butt ground welding It is applied after grounding the surface for good penetration When welding cracks make sure to cross either the upper or lower flanges Weld completely and then grind off excess weld to remove notches or weld buildup on the flange edge Use medium range of electrode current Chassis Best Practices 2010 Plug Welding Plug or ring welds are good for attaching reinforcements because they eliminate the possibility of loose fitting bolts Be car
3. ANEAN EESE N ESEE EASE EAREN 32 Diesel Exhaust Fluid DEP SYSTEM e aAa Eaa EEE 32 E A T A A A A A A E A A ATE 33 General FS E DE rcm 33 Federal Standards and Regulations MM 33 Modification o Oo o 00S 0m 33 Brake Lines34 Parking Brake SYStem M E 34 Electronic Dynamic Rear Proportioning 36 Chassis Best Practices 2010 CHASSIS BEST PRACTICES Index cont d EXHAUST SYSTEM ii pe exinde decia di xb Exhaust Sy Eso C EATEN E AENEAN ROUNO ccr jer c SUSPENSION El ip ee General 2 sn nU REA EY Front 6 e EE E 7 WHEELS AND TIRES 2 Chassis Best Practices 2010 UPPE INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle Frame Extension The frame extension is designed to maintain structural rigidi
4. Chassis Best Practices 2010 Avoid welding closer than 50 8 mm 2 in to this area Doing so could shrink the spring bracket rivets resulting in a loose joint Reinforcement and Weldment Refer to Figures 7 and 8 for clarification throughout this section The illustration in Figure 7 shows an acceptable reinforcement and weldment method The method shown in Figure 8 however is preferred because e The slots are smaller and can be more easily positioned to avoid clearance holes in the frame Chamfered sides diminish stress concentrations in corners which can cause cracks to develop in the weld Use an L shaped reinforcement made of the same material and thick ness as the frame Reinforcement height must allow for the weldment but not exceed the tangent of the radius for the bend at the upper flange of the frame The inside radius of the reinforcement must be smaller than the outside radius of the frame so as to provide a gap at the bend 11 Add holes to the reinforcement to provide clearance for all fasteners rivets or retention clips in the frame sidemember Any frame identification number or VIN which would be lost when the wheelbase is stretched or shortened must be duplicated on the reinforcement or sidemember of the finished frame continued on next page CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d After final welding reapply undercoating to the exposed p
5. Figure 29 continued on next page Ey Uri INTEGRATION RETAINING BEAD HOSE FUEL CLAMP ASSEMBLY CHASSIS BEST PRACTICES Fuel Systems cont d SPLICE JOINT STOP BERD RETAINING BEAD LABEL DIESEL FUEL ONLY HOUSING FUEL TANK HOSE FUEL VENT HOSE FUEL Figure 30 Fuel Tanks After conversion is complete the fuel system must be fully Diesel powered vehicles incorporate a water drain functional Do not modify the fuel tank or use non OEM fuel provision in the fuel system Do not open these tanks on any ambulance vehicles Use only specific OEM not valves except to siphon water and contaminants from aftermarket fuel caps Provide minimum clearance of 51 mm the fuel system 2 in between the fuel tank and the top front rear and sides of body and other supports Tank may be pressurized to 1 25 PSI maximum to check for final line leakage or for forcing fuel through the system Other recommendations are Pressures greater than this amount may be detrimental and e Do not apply undercoating to fuel tanks affect tank durability e Make sure to point bolts screws and other potentially damaging objects away from the fuel tank Shield all such projections to help maintain fuel system integrity in the event of a vehicle crash Chassis Best Practices 2010 INTEGRATION CHASSIS BEST PRACTICES Auxillary Fuel Tanks amp Diesel Exhaust Fluid DEF System Auxil
6. qut dC aaaeaii 21 Body Mounting Fasteners TNNT TEES 22 Prevailing AKETE EEEE EEE EE EES 23 Recommended Body Mounting 23 Type 1 U Bolt Threaded Rod End Plate Rt pls 23 Type 2 Brackets and Pinch 23 3 Rigid Mounting Service Utility 2 23 Type 4 Shear Plate Mounted E 23 NTEA Body e NER m 24 Shear Mc EE TO OO S DOE 28 FUEL SYSTEMS 29 mz m ee eal E mU EE 29 SUUM IRIURE eee 30 E E E 31 Auxiliary Fuel
7. Before stripping the vehicle down for repair make sure to support the frame on a smooth level floor This will permit frequent checking for alignment during the straightening and replacement process continued on next page peii CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d INTEGRATION Driveshaft Propshaft Extension The driveshaft can be extended using a single length or multiple piece driveshaft It is important to develop and follow proper design and installation guidelines for this process Driveshaft Extension Design The most important objective is to design driveshaft extensions that efficiently transfer power from the transmission to the rear axle assembly Figure 15 For higher durability and reliability General Motors recommends using only graphite driveshafts manufactured with driveline tubing Chassis Best Practices 2010 SLIP YOKE FRRME RSSEMBLY PROP SHRFT CENTER BERRING UNIVERSRL JOINTS Figure 15 PINION REAR AXLE PINION REAA AXLE PROP SHAFT CENTER BESRING continued on next page CHASSIS BEST PRACTICES HUM Extending Wheelbase Moving Axle cont d Two Piece Driveshaft Bearings SVMs should devise a gauge by which to measure driveshaft For two or three piece driveshaft applications use an in line bearing alignment angles for front and rear shafts For smooth operation assembly Figure 16 shows a typical two piece dri
8. 4 Shear Plate Mounted This mounting type is used to attach non rigid subframes to OEM frames Figure 23 Non rigid body types include platform stakebed dump rollback carriers and open top grain livestock bodies Ey Uri INTEGRATION 16 66 MM 0 66 IN TYPICAL si 25 4 1 0 IN MIN 25 4 MM 1 0 IN MIN 50 8 MM 1 25 4 MM 1 0 IN MIN SHEAR PLATE 9 5 0 375 IN THICK HOT ROLLEO CHASSIS BEST PRACTICES Body Mounting cont d Torsionally Flexible Bodies 9 5 MM 0 375 IN MIN THICK HOT ROLLED STEEL 2 HOLE Bodies with wood metal sill construction are considered FROM TOP OR BOTTOM OF torsionally flexible When mounting torsionally flexible bodies consider the following points SEAR PLATE The sill should rest directly and squarely on frame side rails O IN MIN SECOND UNIT BODY STRUCTURE Wood sills must be chamfered 13 mm 0 5 in at the front end tapering to meet the frame approximately 300 mm T 11 8 in from front end of sill see Figures 24 and 25 STEEL 4 HOLE ATTACHMENT TO CHASSIS FRAME 76 2 3 0 IN MIN FROM REAR AXLE SPRING HANGER OR END OF FRAME PTN NUT OROUE 82 88 5 NM 60 65 ir A ji 1 19 66 IN DIAMETER HOLES 57 2 MM 2 25 IN MIN FROM TOP OR BOTTOM SURFACES OF CHASSIS FRAME CFORWARD OF REAR AXLE 44 5 MM 1 75 IN MIN FROM TOP OR BOTTOM SURFACES OF CHASS
9. apart in web area only not in top bottom flanges For holes drilled forward of the rear axle make sure their centers are no closer than 63 5 mm 2 5 in from the top or bottom flanges and 89 mm 3 5 in from any suspension attachments For holes drilled rearward of the rear axle the centers must be at least 51 mm 2 0 in from the top or bottom flange and 89 mm 3 5 in from suspension attachments UPPE INTEGRATION CHASSIS BEST PRACTICES Fuel Systems The fuel system includes the fuel tank metering lines including purge control solenoids and canister s Proper sealing is critical to the integrity and overall operation of the fuel system The SVM assumes complete responsibility for any modifications or alterations to the fuel system This includes responsibility for system reliability and performance as well as compliance to FMVSS 301 CMVSS 301 General Motors recommends that SVMs DO NOT ALTER THE FUEL SYSTEM IN ANY WAY When delivered the vehicle fuel evaporative emission control equipment is certified in compliance with Federal and California Vehicle Emission Standards Any alteration to systems or components and their location could void compliance Systems include Fuel tank metering unit lines including purge control solenoids and canister or canisters Environment Includes e Heat sources heat shields system component relocation Fuel Fill General Motors recommends the following fuel f
10. as shown earlier in Figure 2 to prevent possible error Use the following procedure for splicing the frame 2 Grind cut edges of the frame smooth for line to line fit This ensures a good fit and clean metal surface for the welding operation Frame inserts must be the same dimensional shape metal gauge thickness material type and yield strength as the original frame side member FRAME INSERT 1 2 THICKNESS Figure 3 continued on next page Chassis Best Practices 2010 PvR CHASSIS BEST PRACTICES INTEGRATION Extending Wheelbase Moving Axle cont d 6 Tack weld runoff blocks to the edge of the upper and lower 7 Butt weld the outside edges of the frame insert to the frame flanges of the frame and frame insert Figures 5 and 6 Grind visible welds on both sides to parent metal This helps to eliminate joint edge burnout and prevent joint 8 Butt weld the outside of the joint with a single pass movement during butt welding vertical up Figure 5 Butt welds on the inside surface of the frame should also be done with a single pass Figure 6 Butt Weld Outside of Joint 1st WHERE POSSIBLE USE EXISTING FRAME HOLES TO BOLT FIXTURE IN PLACE FRAME INSERT C CLAMP TO FIXTURE PRIOR TO WELD OPERATION WELD VERTICAL FRAME FIXTURE RUN OFF BLOCK DISTANCE BETWEEN ORIGINAL REFERENCE MARKS INCREASED BY DESIRED WHEELBRSE EXTENSION Figure 5 Figure 4 Butt Weld Inside of Joint 2nd W
11. as smoothly as possible make sure that the input universal joint is approximately equal and opposite to the output universal joint angle That is the downward angle a of the transmission output shaft relative to the driveshaft axis must be equal to the downward angle b of the pinion as shown in Figure 18 Note Angles shown are exaggerated for clarity To allow the best compromise for the pinion angle as it changes because of vehicle loading acceleration and ride motion these angles are determined and set at the factory This eliminates the need for adjustment by the SVM Universal joints are designed to operate safely and efficiently within a 3 degree joint angle Exceeding this design limit may break the joint or cause excessive driveline vibration Multiple Piece Driveshaft Alignment Procedure The bearing supporting the driveshaft must be positioned vertically and laterally so that driveshaft segments are all in a straight line between the transmission output yoke and differential input flange The following recommended procedure should enable SVMs to properly align the driveshaft regardless of build variation STRING For vehicles requiring more than one bearing support perform this procedure for each bearing 1 After extending the vehicle install the driveshaft bearing support crossmember without the driveshaft or support bearing 2 Position the vehicle on a drive on hoist or otherwise allow it to rest fully on
12. corrosion protection removal refer to Leave corners bends and radii free to flex Welding in these locations Altering the Wheelbase on page 3 in this section creates stress risers that can often lead to cracks in the weld Do not weld at the lower flange of the frame either on the flange or at the edge For the final weld operation fillet weld the reinforcement slots or holes to the frame It is acceptable but not necessary to fillet weld the entire circumference of the slots or holes Adding a fillet weld on the bottom half 180 degrees only will provide sufficient strength continued on next page Chassis Best Practices 2010 CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Holes The illustration shows a channel section siderail loaded vertically as a beam This type of loading stretches the lower half of the section and compresses the top half as indicated by the arrows There are two holes in the lower half the uppermost of which is located about one third of the rail depth up from the bottom flange Stress at the bottom of this hole is approximately equal to the stress in the flange Any hole located less than this distance from the bottom flange will have significantly higher stress than the flange Figure 10 illustrates these principles more specifically It is important to locate holes in the least critical area possible In high load areas place holes near the neutral axis
13. have already incorporated clamped attachments into their designs because of these benefits Since U bolts and clamping devices depend on friction and a maintained clamping force for attachment a positive bolted connection should also be used for security Bolted attachments are generally preferred over welding because they retain more strength and are more easily serviced Chassis Best Practices 2010 PREVAILING TORQUE NUT PTN U BOLT PLATE U BOLT U PLRTE U BOLT MOUNTING Body Mounting Fasteners SVMs should observe the following recommendations for body mounting fasteners Use PTN fasteners instead of double nuts Provide maintenance labels decals wherever practical Shear plates should be located at rear of frame rail and body longitudinal crossmember Attachment aft of rear spring rear shackle bracket Use steel not wood anti crush fabricated vertical spacers to protect flanges Use Grade 8 bolts PTN nuts on shear plates Choose elastomeric rubber that meets critical damping requirements Do not weld in high stress areas continued on next page UPPE INTEGRATION CHASSIS BEST PRACTICES Body Mounting cont d Prevailing Torque Nuts PTN Prevailing torque nuts PTN have an interference fit on the threads The interference fit prevents the nut from loosening after it is tightened eliminating the need for cotter pins or lock washers PTN fasteners are recommended for several bod
14. of the side rail or horizontal center line of the web The illustration in Figure 9 was taken from a laboratory test conducted to study stress at a hole under beam loading In this test the section was covered with photo stress plastic which shows stress through color fringes when viewed under polarized light Figure 9 continued on next page Chassis Best Practices 2010 CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d To avoid premature failure SVMs should observe these general guidelines VERTICAL LORDING Use existing holes wherever possible Locate holes no closer to the top or bottom flange than existing holes placed by the chassis manufacturer e Avoid placing holes in the lower one third of the web in the area immediately behind the cab Crossmembers Additional frame crossmembers are required whenever a two or FLANGE NOTCH TLR three piece driveshaft is used to support the center bearing and shaft STRENGTH Crossmember design should meet the following criteria Adequate vertical stiffness to prevent resonance with prop shaft 38 imbalance excitation in the vehicle speed range RADII 6 98 MM 0 275 IN Adequate strength to support the weight of the prop shaft and support bearing with respect to maximum vertical acceleration WEB HOLE of the prop shaft Note Crossmember has adequate strength if LATERAL LOADING stiffness requireme
15. through a nearby hole in the frame flange continued on next page UPPE INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Improper welding or welding methods are a major cause of stress concentration points which may ultimately result in frame failure Refer to general welding instructions outlined under Welding on page 13 in this section Reinforcements Using improper reinforcements or attachment methods may create localized stress concentrations This may actually reduce the frame load carrying capacity to below that of the original frame i e before adding reinforcements There are five basic types of reinforcement see Figure 11 Their descriptions follow INVERTED LT STRAP REINFORCEMENT Figure 11 Chassis Best Practices 2010 Upright L reinforcements should be used in maximum stress locations at the bottom of the lower flange and where buckling of the upper flange is not a problem They may be placed either inside or outside the frame side rail The upright L reinforcement is quite versatile and may be used as full length or short localized reinforcement However it may be limited by the configuration of the frame or spring hanger brackets Inverted L reinforcements also may be used inside or outside of the frame rail They are recommended where maximum stress is transferred to the upper flange for example dump trucks with the box in th
16. ELD VERTICAL UP Figure 6 continued on next page Chassis Best Practices 2010 Ey Uri INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d FRAME INSERT D 152 0 MM 6 0 IN OVERHANG 50 0 MM 2 0 IN i 9 75 IN E Gl INO 3E INFORCEMENT FRAME 8 5 MINIMUM seePnoxinarELY 152 0 5 0 IN ADJUST TO MISS CLEARANCE HOLES Je A A FILLET WELO TO FRAME USE APPROPRIATE RADIUS TO ALLOW GAP Figure 7 Variations in equipment and welding materials make it difficult to recommend specific amperage electrode specifications and welding speed Therefore SVMs should have a qualified welder or consulting service establish and test this procedure Standard industrial practices apply 9 Visually inspect all welds for defects This will ensure high quality welds which are critical to joint integrity 10 Remove runoff blocks and chip or grind the joint smooth The out side surface of the frame weldment must be as smooth as the rest of the frame to allow flush fit for reinforcement attachment Make sure that grind marks are parallel to the length of the frame The finished joint should be of the same thickness as the sidemember The outer reinforcement length is defined by the splice location and length of the insert with a minimum 152 mm 6 in overlap on each end The reinforcement must not encroach on the rear leaf spring front hanger bracket
17. Factory installed OEM tires and wheels are designed to operate up to full load capacity when tires are inflated to specification Other recommendations are Use only the OEM wheels on any ambulance vehicle The OEM lug nut bearing surface should not retain any wheel trim such as wheel simulators Check wheel lug nuts for proper torque For torque specifications see the Owner Guide Check tires and inflate to recommended tire pressure Refer to either the vehicle s tire inflation label or the Owner Guide For wheel maintenance guidelines refer to the appropriate GM Service Manual
18. IS FRAME CREARWARD OF REAR AXLE The NTEA Body Practices types in terms of torsional basic categories Non rigid Semi rigid Rigid Super rigid The degree of rigidity determines the appropriate attachment method The table below li body types Chassis Best Practices 2010 TYPICAL 25 4 MM 1 0 IN MIN FILLER STRIP OR SPACER AS REQUIRED CHASSIS FRAME REAR AXLE SPRING HANGER L 15 9 0 625 IN DIAMETER GRADE BOLTS PTN NUTS TO ATTACH SHEAR PLATE TO CHASSIS FRAME AND SECOND UNIT BODY STRUCTURE Figure 23 Rollback Carriers NTEA Body Classifications Refuse Packers Subcommittee defines vehicle body Tank rigidity grouping them into four sts the torsional rigidity of selected Service High with Top Low without Top Platform Dry Freight Van Body Rollup Door Swing Door Refrigerated Bodies Dump Bodies Wreckers Recycling Sorters Torsional Rigidity Of Selected Body Types Body Mounting Non Rigid Semi Rigid Super Rigid Grain Livestock Open Top Livestock Closed Multideck Spreader Feed Seed Fertilizer Determined by Manufacturer continued on next page CHASSIS BEST PRACTICES INTEGRATION Body Mounting cont d APPROXIMATELY 324 8 12 0 PTN NUT METAL CHANNEL ATTACH TO SILL WITH WOOD SCREWS OR NAILS CLIP PLATE L 12 7 MM 9 5 IN CUT OUT TO CLERR WIRING OR TUBING Figure 24 CLI
19. P PLRTE e PTN NUT CLIP PLATE FILLER BLOCK FRAME SIDE RAIL 70 BOLT FILLER BLOCK CLIP PLATE CLIP PLATE PTN NUT OPTI y OPTIONAL U BOLT PTN NUT STUDS MOUNTING FRAME SIDE RAIL Figure 25 Chassis Best Practices 2010 LONGITUDINAL SILL PTN NUT SPACER BLOCK ATTACH TO SILL WITH WOOD SCREWS FILLER BLOCK CLIP PLATE PTN NUT FILLER BLOCK WOOD SILL SPACER STEEL SILL CONSTRUCTION continued on next page CHASSIS BEST PRACTICES Body Mounting cont d Sills must not overhang outside of frame If wood sill is brackets must have a clearance of at least 5 mm 0 18 in not as wide as frame flange install spacer blocks at hold before final attachment of shear bolt see Figure 26 On down Wood grain of blocks should be parallel up and bodies with steel sills upper shear plate bracket may be down with hold down bolted or welded to sill Clearance between upper and lower Shear plate fasteners 13 mm 0 5 in minimum diameter brackets should be a minimum of 1 5 mm 0 06 in before must be located near rear of body sills On bodies with final attachment of shear plate Installing shear plates is wood sill construction upper and lower shear plate optional with steel body sills UPPER SHEAR PLATE BRACKET REINFORCING LOWER SHEAR PLATE BRACKET ae SECTION A A Figure 26 Chassis Best Practices 2010 continued on next p
20. U I Body Builders Manual continued on next page pipi CHASSIS BEST PRACTICES Fuel Systems cont d Fuel Lines When adding components near the fuel line area be sure to provide a minimum clearance of 305 mm 12 in to the exhaust system or install a protective metal shield Use only GM approved fuel line assembly suppliers and components Replace damaged fuel lines Never attempt to use or repair a fuel line that has been kinked General Motors also recommends the following precautions e Be careful not to bend fuel lines and avoid routing them near sharp edges and protruding objects Clip fuel lines to chassis spacing the clips every 600 mm or less Metal clips should have plastic or rubber liners Use corrosion resistant steel tubing with short sections of approved electrically conductive hose to connect components Steel tube ends should be beaded for hose retention Replace the entire tube at the new required length Do not cut See Fuel Line Material specification UNSG10080 UNSG10100 Cold Rolled Steel also identified as GM 124 M Anin tank pump pressurizes the fuel supply Do not use coupled hose nylon quick connects or clamped hose Make sure that fuel return system lines are not blocked and hoses not pinched e Before adding extensions clamp remaining fuel lines to prevent contamination during vehicle conversion Figure 30 Avoid exposing fuel system components and lines to high temperatures such as tho
21. aced bolt pattern to holes already exist in the frame flange attach this type of reinforcement to the web Stagger plug welds in a 203 254 mm 8 10 in pattern when Attaching Reinforcements attaching reinforcements to the web section Procedures for attaching reinforcements may vary depending Figure 12 on materials However SVMs should observe the following general guidelines n some cases it is permissible to plug weld strap reinforcements to the flange at 152 203 mm 6 8 in e General Motors recommends attaching reinforcements intervals to increase section modulus Note This is a highly with Grade 8 bolts and hardened flat washers not rivets specialized procedure and should be performed by only because most field service outlets do not have proper fully trained personnel riveting equipment PLUG PATTERNS OF STRAP REINFORCEMENTS 203 2 254 90 8 0 10 0 IN 203 2 254 0 MM 8 0 10 0 IN 152 4 283 2 MM 6 8 8 0 IN WEB REINFORCEMENT STRAP REINFORCEMENT Figure 12 continued on next page Chassis Best Practices 2010 UPPE INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Terminating Reinforcements To prevent localized stress concentration reinforcements must be properly terminated Reinforcement ends must be tapered or stress relieved Tapers should not exceed 45 degrees When using several reinforcements together stagger them so that t
22. age Funds Chassis Best PRACTICES You Body Mounting cont d Rabbet grooves at the top of longitudinal wood sills Figure as possible one near the rear end and others should be 27 to allow sheet metal channels of 1 7 mm or No 14 spaced as nearly equally as possible between front and rear gauge minimum at each mounting Use 6 mm 0 25 in mountings Do not mutilate the frame side rails in any way minimum flat plate Metal channels or flat plate should extend to accommodate mountings Use clip plates approximately the same thickness as On non steel sill bodies use a hardwood spacer between mounting bolt diameter at top and bottom of mounting the sill and frame side rail The spacer must be at least bolts When U bolts are used the contour at top of the 19 mm or 0 75 in thick i e chamfered 13 mm 0 5 in at U bolt should fit against the clip plate Plate may be the front end tapering to meet frame 300 mm 12 in A notched instead of using holes refer back to Figure 25 Wood spacer is not necessary if steel sill body is used Use a block of hard dry wood with grain running up and approximately 25 mm 1 in beyond the clip plate Mountings must be spaced to clear suspension and any down between flanges of frame side rail at each mounting other parts attached to frame side rail Use two long Block should extend beyond width of frame flanges and bolts studs or U bolts 13 mm 0 5 in minimum diameter should be grooved Mounti
23. ake Performance FMVSS CMVSS 106 Brake Hoses Hydraulic Air and Vacuum FMVSS CMVSS 116 Motor Vehicle Brake Fluids For additional information refer to the following SAE specifications SAE J1401 Road Vehicle Hydraulic Brake Hose Assembly Use with Non Petroleum Base Hydraulic Fluids SAE J1288 Packaging Storage and Shelf Life of Hydraulic Brake Hose Assemblies SAE J1403 Vacuum Brake Hose SAE J1406 Application of Hydraulic Brake Hose to Motor Vehicles Chassis Best Practices 2010 Modification Checklist For vehicle specific diagnostic inspection and service guidelines refer to the appropriate GM Service Manual The following checklist will also help SVMs to ensure proper brake system operation after modification Do not splice the park brake cable Make sure the hydraulic brake system is free of air and hydraulic leaks Bleed brakes if necessary Ensure that the vacuum booster system or hydroboost system is functional and free of leaks Check the master cylinder fluid level Fill as necessary Check the power steering fluid level on vehicles equipped with hydroboost brake Make sure that added floor carpeting does not restrict service or parking brake pedal travel Provide at least 51 mm 2 in clearance between body or chassis mounted components and brake hoses Never change the brake main cylinder location brake pedal pushrod length or pedal position Verify that the brake warning switch i
24. an and can exceed 1 600 F with slightly lower pipe surface frame Figure 33 temperatures When adding body components near e When conversion is complete check for leaks and the exhaust system be extremely careful to choose restrictions in the exhaust system Figure 34 Repair as components with the appropriate temperature ratings or required provide shielding For additional information on exhaust pipe installation refer to the GM Body Builders Manual PIPE SHIELD MUFFLER ASSEMBLY IPE MUFFLER OUTLET MUFFLER ASSEMBLY HANGER Figure 33 next Chassis Best Practices 2010 co ued on next p age UPPE INTEGRATION CHASSIS BEST PRACTICES Exhaust System cont d Routing When determining exhaust routing locations be sure to consider the thermal expansion of the extension area Additional guidelines are Tailpipe extensions must extend at least 51 mm 2 in outboard of the body side panels Added exhaust hangers should allow expansion without binding up Do not locate tailpipe exit forward of the rear wheels Test tailpipe location with the vehicle standing still and in motion to ensure that exhaust gases do not enter the passenger compartment through side or rear windows or underbody seams and holes Weld all connections when adding extensions to existing exhaust systems Use GM approved sealers at all slip joint connections except at the catalytic converter Do not rou
25. are Parking Brake Systems If so equipped the vehicle s mechanical parking brake system with automatic vacuum release consists of parking brake pedal assembly vacuum diaphragm cables and connectors Figure 32 The parking brake system should be able to withstand at least 400 Ibs of cable tension General Motors recommends using a one piece parking brake cable assembly consistent with the base vehicle For adjustment and testing procedures following installation refer to the appropriate GM Service Manual Avoid special vehicle designs e g ground effects packages that may prevent proper brake system ventilation Lack of ventilation may lead to shortened brake life FRAME ASSEMBLY CABLE AXLE REAR SPRINGS REAR AXLE Chassis Best Practices 2010 Allow at least 17 mm 0 7 in clearance between brake lines and moving components e g steering shaft shift levers etc Allow 13 mm 0 5 in clearance between brake pipes and vibrating parts e g front sheet metal underbody and power brake booster unless pipes are clipped to these components Use brake line clips spaced at intervals no greater than 762 mm 30 in Do not splice parking brake cable Replace with new cable at required length only Figure 32 22 wr WASHER em SHOCK BRRCKET REAR AXLE CABLE AXLE continued on next page CHASSIS BEST PRACTICES Brakes cont d Electronic Dynamic Rear Proportion
26. ation of noise abatement components place the vehicle in violation of federal state or local noise laws The SVM may have to recertify vehicle compliance with federal state and local noise emission requirements The SVM must assume full responsibility for complying with Environmental Protection Agency EPA noise regulations if the exhaust system is modified The U S Environmental Protection Agency EPA has established noise emission standards applicable to vehicles in general vehicles in excess of 10 000 pounds GVWR capable of transportation of property on a street or highway manufactured after January 1 1978 under the provisions of the Noise Control Act of 1972 The standards provide that vehicles manufactured after January 1 1978 when tested pursuant to EPA s prescribed test procedure must conform to an 83 dBA level and vehicles manufactured after January 1 1988 must conform to an 80 dBA level The Act and the standards impose legal obligations on vehicle manufacturers and subsequent manufacturers Questions dealing with what is covered under the definition of Chassis Best Practices 2010 a vehicle in the standards and the specific application of the Act or the standards to your business should be discussed with your legal counsel This is particularly so in light of EPA s broad definition of a vehicle The standards or interpretations of such standards are subject to change by the EPA New standa
27. below the frame rail DEF tanks do not have a drain Service procedure must be followed if contaminated remove and drain DEF Tank cannot be moved on full body vehicles FMVSS301 Def Fill Hose Assembly e Increasing the length not recommended Shorten from tank end is preferred DEF fill location to always be above tank gravity fed 4 degree angle min with minimal bends Fluid Delivery Line This line is heated do not cut or adjust length e Carefully coil any extra line and secure to maintain the as shipped heated line length Use GM clip part 425952656 Wire Harness e Do not change modify the wire harnesses on the DEF tank e Carefully coil any extra line and secure UPPE INTEGRATION CHASSIS BEST PRACTICES Brakes Brakes General Requirements SVMs must ensure that the brake system functions properly after conversion is complete Modifying or altering the brake system may require the SVM to recertify compliance with FVMSS 105 and CMVSS 105 Modifications may also adversely affect the vehicle s braking capacity Avoid designs such as special ground effects packages which may prevent proper ventilation of the brake system Also avoid changing the brake main cylinder location Federal Standards and Regulations Brake systems must conform to all federal motor vehicle safety standards and regulations including FMVSS CMVSS 105 Hydraulic Service Brake Normal Emergency and Parking Br
28. bility performance and compliance to applicable FMVSS requirements This section outlines GM recommended procedures and precautions for proper installation of special bodies and or equipment on frames Failure to follow these recommendations could result in serious damage to the basic vehicle Flanges GM does not recommend drilling holes in frame flanges Drilled holes in frame flanges will reduce fatigue life significantly See Figure 10 page 9 Holes When drilling holes for mount brackets supports and outriggers in the frame rail vertical side wall SVMs should observe the following recommendations Material between the edge of the hole and inside of upper or lower flange must not be less than 37 mm 1 5 in The minimum edge distance between any two holes must be larger than twice the diameter of the larger hole No hole should exceed 20 mm 0 75 in in diameter continued on next page Chassis Best PRACTICES Extending Wheelbase Moving Axle cont d Altering The Wheelbase Avoid altering chassis wiring When shortening the wheelbase Frame Splice Location simply secure a gentle bend or loose coil in the wiring General Motors recommends splicing in a straight segment of the Avoid cutting on uneven sections of the frame such as frame frame rail just forward of the rear spring front hanger bracket see forms or irregular bends and depressions Figure 1 This is the optimum location for maintain
29. d height above the frame and isolate the compartment from underbody crossbars For optimum load distribution isolation noise and vibration Use full floating automotive style rubber additional body mounts should be no farther apart than body mounts or other chassis manufacturer approved body 762 mm 30 in When designing and locating body mounts mount systems For bodies up to 3708 mm 146 in in length SVMs should also consider serviceability and the recom install a minimum of four per side for longer bodies at least mendations outlined in the General Requirements section five per side that follows General Requirements To maintain base vehicle performance it may be necessary to add change or move body mounts along the frame General Motors recommends the following practices for SVM added body mounts Use only GM or equivalent body mounts Use OEM rubber body isolators frame body rails and or outrigger brackets on the frame vertical side web Avoid mounting bodies directly to the top of the frame Doing so restricts frame torsional flexibility It may also promote body cracking and provide a direct path for chassis noise vibration and harshness NVH Figure 20 shows typical body mounts Never weld body supports directly to the frame flanges Do not weld body structures directly to frame extensions behind the rear suspension Use consistent body attachment methods along the entire frame length Use reinforcements or fill
30. dure Pipes wiring conduits and any other related components specifications and measurement of the A dimension must not be placed where they cross the path of motion of under Diagnosis and Front Alignment sections the rear axle driveshaft axle brake pipes hoses spring or tires Such crossing could result in rupture wear through or separation due to normal axle motion Customer notification may be required in some states if chains cannot be used Chassis Best Practices 2010 CHASSIS BEST PRACTICES Wheels And Tires Since May 1971 National Highway Traffic Administration regulations have required manufacturers to maintain specific information on tires This information is used to notify consumers of defective or non conforming tires The SVM should consult with an attorney regarding how these regulations apply In compliance with these regulations General Motors keeps records on tires installed on each vehicle it ships It is important for the SVM to ship the vehicle with OEM tires Any tire removed from the vehicle during conversion should be replaced The SVM is responsible for keeping records on any tire changes made during conversion All data must correspond to the correct vehicle identification number VIN For specific information refer to Federal Regulation 574 Chassis Best Practices 2010 All tires must meet FMVSS 120 CMVSS 120 new tire and rim selection regulations
31. e frame side rail Use spring loaded angle type mountings Figure 28 They may be bolted or welded to the body sill However always use bolts to attach them to the frame side rail Do not weld directly on the frame side rail Position mountings to allow a clearance of at least 6 mm 0 25 in between upper and lower brackets Use SAE Grade 8 or Class 10 9 metric bolts with PTN nuts Spring loaded mounting bolts also require PTN nuts The springs should be as short as practical allowing preloading which will help prevent excessive body during operation and a minimum of 25 mm 1 in at the front of the body before becoming solid Trunnion type body mountings also provide flexibility and are acceptable substitutes for the spring loaded type Locate bolts 13 mm 0 5 in minimum diameter near the rear of the body sills Before final attachment make sure to allow clearance of at least 1 5 mm 06 in between upper and lower shear plates Chassis Best Practices 2010 BODY SILL BODY GUIDE TOP OF FRAME PLATE SPRING BOLT ie eem WEAR PLATE FRONT OF VEHICLE BOTTOM OF FRAME Figure 28 Shear Plate Attachments Whenever possible use existing holes to attach shear plates to the frame side rails When additional holes are required make sure they are no larger than 20 mm 0 75 in in diameter Drill holes at least 63 5 mm 2 5 in
32. e raised position This type of reinforcement is easily adapted to frame and hanger bracket designs which prohibit using an upright L reinforce ment or where the upper flange is subject to buckling Channel reinforcements can be used for full length or localized reinforcement and can be installed inside or outside the frame side rail Two major disadvantages are their added weight and required installation time It may also be difficult to place the channel inside or over the existing rail due to manufacturing tolerances crossmembers or mounting brackets Strap reinforcements may be used to increase the section modulus of a frame that has been weakened by prior damage and repair In such cases strap reinforcements provide the additional modulus required to return the frame to its original strength Strap reinforcements are plug welded at intervals of 152 to 203 mm 6 to 8 in Plug welds must be no closer than 19 mm 0 75 in to the edge of the frame flange Do not weld across the end or along flange edges Edges should be cut at an angle continued on next page CHASSIS BEST PRACTICES INTEGRATION Extending Wheelbase Moving Axle cont d Inverted J reinforcements are designed to increase flange Do not attach reinforcements except strap type to flanges strength and prevent flange buckling under high torsional except in cases where mounting bracket or crossmember inputs or shock loading Use only a sp
33. eful however to properly place plug welds in different types of reinforcements GM highly recommends E 7018 electrode for plug welding because of its good pene tration and light coating Use high range of electrode current and appropriate voltage for flat or vertical plug welds Overhead plug welding is very difficult Do not use this method unless other approaches are impractical Then use high range for first pass and complete plug at medium range Refer to plug weld table Figure 13 for hole size to use for material thickness variations Stitch Intermittent Fillet Welding This type is also called transverse or longitudinal fillet It is not generally used on frames because continuous fillet welding provides better attachment Stitch weld when warp and heat control is critical using medium range of electrode chart For all types of welding make sure to e Connect welding machine ground cables as close to work area as possible Use smaller diameter electrode whenever possible and make several passes rather than large diameter and single passes Vehicle load capacity depends on strength and rigidity For effective repairs make sure that frame service is performed only by qualified personnel using proper materials and equipment Dissimilar Metals To prevent a chemical reaction apply a barrier coating of good corrosion inhibiting compound to all faying surfaces of dissimilar metals Remove old sealer with a putty knife
34. er blocks where mounting devices may deform frame flanges Mounting devices must be locked units that minimize loosening but can be retightened if necessary Use grade 8 PTN nuts Correctly position all body mounts directly under cargo body Figure 20 crossmembers or longitudinal members to prevent body fatigue failures continued on next page Chassis Best Practices 2010 CHASSIS BEST PRACTICES INTEGRATION Body Mounting cont d Design body mounting schemes that comply with recommended GM guidelines see GM Body Builders Manual NTEA Industry Standards and Federal Government Mil Std Specifications Body Mounting Considerations To ensure ease of maintenance and service SVMs must provide access to frame crossmember located over the transmission rear shock absorber crossmember all batteries and the fuel tank There should also be adequate clearance between the rear tires and the body structure to prevent interference with suspension movement GM also recommends the following Avoid installing equipment such as loading cranes and supplementary tanks on only one side of the vehicle Position body sub frame evenly on the vehicle side rail top flanges Taper the forward ends of the body mounting frame side member to provide a smooth transition to the vehicle chassis frame Avoid using welding straps or other structures between the body and frame that can ground out the elastomeric body mountin
35. g system SVMs should use rubber shock isolation dampers hockey puck discs which are designed for higher control of quality durability squeak and rattle Avoid body mount designs and modifications additions that interfere with travel of the axle or leaf spring up to the full metal jounce position Chassis Best Practices 2010 VERY COMMON MINIMIZES DRILLING BLOCKS MATERIAL JOINT STABILITY PROBLEMS OF SIDEMEMBER OR SILL LOCAL DISTORTION LIMIT CLAMP LOAD USE WIDER CLAMP PLATES BOLTS OR BOLTS CLAMP PLATE Figure 21 Body Equipment Attachment Methods Using U bolts and clamping eliminates the need to drill and weld the frame and is generally the least expensive attachment method When using this method be sure to block the channel side rail to prevent the flange from collapsing when the U bolts are tightened see Figure 21 continued on next page UPPE INTEGRATION CHASSIS BEST PRACTICES Body Mounting cont d SUB FRAME CHASSIS FRAME STEEL OR HARDWOOD SPACER Figure 22 Use spacers between the subframe and the chassis frame as shown in Figure 22 Make sure that spacers do not interfere with plumbing or wiring routed along the frame rail and do not weld them to the frame flanges Metal spacers are preferred as wood can shrink and drop out Clamping devices offer potential savings in both cost and installation time Some equipment manufacturers
36. h the longitudinal mounting rail and the frame at each tie down will prevent the Chassis Best Practices 2010 flanges from collapsing Two guide plates see Figure 23 on page 24 one on each side at the front will prevent lateral shifting of the body This type of mounting is generally suitable for non or semi rigid bodies Type 2 Brackets and Pinch Bolts In this method fabricated and or formed brackets of angles are welded and or bolted to the longitudinal mounting rails and bolted to the chassis frame A bolt pinches the brackets together to secure them A filler cushion or strip preferably of hard rubber may be used between the longitudinal mounting rails and the chassis frame If so it should be secured to prevent loss or movement SVMs should specify the zone or area between the back of the cab and rear axle s where spring mounts should be used Shear plates should be bolted or welded to the body longitudinal mounting rails and bolted to the chassis web but not in top flanges Note Use grade 8 fasteners to secure the shear plates Prevailing torque nuts are preferred in all threaded connections instead of double nuts Type 3 Rigid Mounting Service Utility This category includes industry practice of hard attachment to frame flanges using already existing holes such as the OEM pickup box attachment points It is intended only for vehicles under 15 000 pounds GVWR with service utility bodies Type
37. head Welding 3 32 x 12 20 22 1 8 x 14 20 24 5 32 x 120 190 21 24 3 16 150 240 21 24 Trade Name Source 1132 Die Quench eseese Smith HIGH PERFORMANCE STEEL Trade Name Source Jones amp Laughlin Steel Company PLUG WELD CHART Thickness of Diameter Material Depth of ELECTRODE USAGE WITH FRAME MATERIAL Material 1023 950 High Performance Van 80 Heat Treat Type or Electrode E 7011 E 11016 E 11016 E 7016 E 11018 E 11018 E 7018 Figure 13 Chassis Best Practices 2010 Welding Equipment Never use oxyacetylene to weld frame rails Several different types of welding machines are used to weld on frame rails Following are the three most commonly used machines and their advantages DC Rectifier Type This machine has no moving parts and thus requires very little service The chances of arc blows are also greatly reduced DC Motor Generator Type This machine s principle advantage is its self contained power supply which makes it readily portable It has very good voltage variation control and can be used with all types of electrodes AC Of the commonly used welding machines this is the least expensive It also has a lower possibility of arc blows However the operator may have difficulty striking an arc when using small electrodes For all purpose welding GM recommends using a machine with a 350 ampere minimum capacity
38. heir ends overlap by 203 255 mm 8 10 in Frame Repair and Reinforcement General Rules Specific frame repair and reinforcement procedures vary depending on circumstances and materials The general guidelines outlined here however are very important and apply to virtually all repair and reinforcement situations Always identify the material that makes up the base rail Reinforcement should be of the same or better material than the base rail Make sure that only fully trained qualified specialists perform frame straightening and other repairs Always try to identify the cause of the failure Do not attach fifth wheels or body and accessory mountings through frame flanges Refer to GM Body Builders Manual for additional information Do not drill holes in top or lower flanges Use only proper electrodes as specified for base rail material when welding is necessary Do not use oxyacetylene welding equipment on frames Do not weld reinforcements across the frame flanges Do not weld within 19 mm 0 75 in of the edge of a frame flange Chassis Best Practices 2010 Remove all notches or weld buildups from flange edge when repairing a broken frame Do not weld cast brackets to frame Do not weld flanges of cracked reinforcements and base rails together Do not patch cracks Make correct repair and reinforce the area Always scarf reinforcement ends to provide adequate stress relief Always stagger ends of reinforcements by a
39. iary Fuel Tanks The use of auxiliary fuel tanks is not recommended If an auxiliary fuel tank is added the alterer must take responsibility for compliance with affected motor vehicle safety and emission standards Also if an auxiliary fuel tank is added to a gasoline powered vehicle the fuel must be drawn through a pipe at the top of the tank balance line between tanks is not permitted Venting of auxiliary tank to be provided via purge canister and not to atmosphere Gasoline fueled vehicles are now equipped with a fuel pump return line If an auxiliary tank is added the tank selector valve must include a port which returns fuel to the tank from which the fuel is being drawn Similarly addition of another fuel line for an auxiliary fuel user such as a generator will require emission revalidation In gasoline engines the fuel pump is located in the fuel tank The battery must be disconnected before starting any work on the fuel system Chassis Best Practices 2010 Diesel Exhaust Fluid DEF System The Upfitter is responsible for any modifications to the DEF system Tank Placement e Tank movement is not recommended GM has validated the system durability only in the positions as purchased e The existing DEF tank mounting hardware can not be altered e DEF tank line surface temps cannot exceed 70C proper shielding is required e The DEF tank can not be mounted in a manner which locates the bottom surface of the tank
40. ill guidelines e Fuel tank filler pipe location should be so situated and constructed as to prevent gasoline vapor from emitting to vents of pilot flamed devices Chassis Best Practices 2010 Locate and mount the fuel tank filler pipe so as to prevent vapor from entering the body and engine compartment air inlets Maintain a clearance of at least 76 mm 3 in between the filler pipe vent hose and body components Properly route and secure the filler pipe and vent hoses to prevent failure due to wear and fatigue Make sure that filler pipe vent hose lines have a gravity fuel flow to the tank at all times Verify that there are no fuel traps in the filler pipe or vent hoses Make certain that any added hose is suitable for the type of fuel used gasoline or diesel Provide a ground strap to ensure that electrical ground connection is made Alterations of fuel line routings could affect the completed vehicle and are therefore not desirable The complete fuel system must comply with FMVSS 301 as well as Federal and C A R B vapor emission requirements Fuel Fill Vent pipe hoses should be trimmed to hose retaining beads when present hoses should be secured with approved hose clamps at proper torque specs A minimum of 8 0 inches of fill hose should be maintained between the filler neck and the fuel tank interfaces Fill pipe ends must be free of burrs For additional information on Fuel Fill and Fuel Systems refer to the GM
41. ing DRP Since changes in vehicle mass mass distribution Electronic Dynamic Rear Proportioning DRP allows better and center of gravity determine the appropriate utilization of the rear brakes which reduces brake wear More P oportioning the altered vehicle must not exceed over this better balancing of the brake system as a whole GVWR front and rear GAWR and stay within the improves brake performance allowable center of gravity range Benefits include e Good balance with front brakes when truck is heavily loaded or under towing trailering conditions Provides maximum braking forces at rear wheels Provides maximum braking forces when braking on an uneven road surface such as a washboard at an intersection Reduced front brake wear Better use of rear brakes Improved braking performance Chassis Best Practices 2010 continued UPPE INTEGRATION CHASSIS BEST PRACTICES iy Exhaust System SVMs must be careful to use components and follow procedures that will prevent exhaust fumes from entering any occupant area Observe the following guidelines Seal all holes and openings through the floor and body e Make sure exhaust discharge is unobstructed and directed away from passenger areas With the vehicle in motion test the tailpipe outlet location to ensure that fumes do not enter the passenger compartment Altering the exhaust outlet or its position and removal or alter
42. ing frame strength ide n General Motors highly recommends selecting a cut location and integrity It also maintains minimum weld spacing from hanger e approximately 203 mm 8 in forward of the rear spring front bracket rivet preventing hole rivet shrinkage deformation Other Eas e e If using anoth b on advantages to this location are with the splice zone SVMs should complete stress analysis Requires minimal exhaust fuel brake and electrical modifications Minimizes driveline modification issues from excessive angles and misalignment C K 406 MM 16 90 IN 203 MM 8 0 IN CUT THE FRAME NO LESS THAN 203 MM 8 0 IN FORWARD OF THE REAR SPRING FRONT HANGER BRACKET FRAME SPLICE ZONE Figure 1 continued on next page Chassis Best Practices 2010 PvR CHASSIS BEST PRACTICES INTEGRATION Extending Wheelbase Moving Axle cont d Frame Splice Preparation 3 Choose a Cutting location that will be able to withstand any outer reinforcements that will be added in later operations The reinforcement should extend beyond either end of the 1 Di Eisen biered a not frame insert by a minimum of 152 mm 6 in 4 Scribe or mark the frame for cutting Figure 2 Record all already done ge dimensions for gauging or fixturing on the Frame Splice 2 All OEM frames are dipped in wax for improved Process Check L i
43. minimum of 203 mm 8 in apart Before welding disconnect negative battery cable to prevent possible electrical damage to generating system Welding Welding is an excellent attachment or repair method SVMs however must be very careful to use proper welding procedures Inferior welds and improper methods can cause further frame damage and additional reinforcements may be required later to prevent the problem from reccurring Refer to the specifications table in Figure 13 for proper welding electrode identification and usage Prior to any welding disconnect all negative ground cable s from all battery ies continued on next page CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Uri iid INTEGRATION FRAME SPECIFICATIONS ELECTRODE CHARTS S A E 950 HIGH STRENGTH LOW ALLOY STEEL Electrodes E011 7016 7018 E 11016 E 11018 Trade Name Type Source Great Lakes Steel Flat Welding Jalten 1 Jones Laughlin Available Current Arc Steel Company Sizes Range Voltage Republic Double Republic Steel 5 64 x 9 20 22 Strength Company 3 32 x 12 sess 21 23 Republic 50 1 8 x 14 21 23 5 32 x 14 125 165 22 24 3 16 x dase 160 200 22 24 7 32 x 18 200 250 23 25 uM 1 4 x 18 250 320 23 25 Manganese 5 16 x 18 325 400 24 28 Ti Ten Republic Steel Company Youngstown Steel amp Tube Company U S Steel Bethlehem Steel Company U S Steel Over
44. ng conditions e g potholes by mounting heavy duty frame cross members between the driveshaft and the road surface The driveshaft should be dynamically balanced at 25 65 mph 40 105km driveshaft installation and service Use only General Motors or equivalent parts for Chassis Best Practices 2010 For additional information refer to SAE J901 Universal Joint and Driveshafts Terminology Application Universal Joint Angles and Phasing When an ordinary universal joint is operated at an angle the driven yoke fluctuates slightly in speed as the joint rotates That is although the driving yoke rotates at a constant speed the driven yoke speeds up and slows down twice per revolution This fluctuation of the driven yoke is in direct proportion to the angle through which the universal joint is operating The greater the angle the greater the fluctuation This fluctuation and resulting vibration can be eliminated by phasing the universal joints at each end of the shaft so that the alternate acceleration and deceleration of one joint is offset by equal and opposite accelerations of the other joint Correct phasing is achieved by aligning the universal joint lugs on each end of the shaft refer back to Figure 17 continued on next page UPPE INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Universal Joint Angles and Phasing cont d To allow the propshaft to operate
45. ng bolt fitted into groove will hold for each mounting One mounting should be located at block in place Where steel body sills are used a similar the front end of sill at or as close to rear end of taper block is required between sill flanges 2 CHANNEL FLAT PLATE 6 4 MM 0 25 IN WOOD RRBBET SILL GROOVES CN SPACER LONG I TUD INAL LONGITUDINAL WOOD SILL WOOD SILL WOOD SSR SS WOOD SCREWS SCREWS METAL CHANNEL CONSTRUCTION FLAT PLATE CONSTRUCTION Figure 27 Chassis Best Practices 2010 continued on next p age UPPE INTEGRATION CHASSIS BEST PRACTICES Body Mounting cont d Torsionally Rigid Bodies Because of their solid construction torsionally rigid bodies require more flexible mounting Spring loaded body mountings provide optimum frame and body life When mounting a body of this type SVMs should follow these guidelines Use a hardwood spacer with a minimum thickness of 19 mm 0 75 in between the body sill and frame side rail Make sure the spacer is chamfered 13 mm 0 5 in at the front end and tapered to meet the frame approximately 300 mm 11 8 in from the front end of the spacer Use a body guide ribbed for extra strength as shown in Figure 28 to restrict lateral movement of the body and relieve shear stress on mountains Bolt or weld the body guide to the body sill near front end of the body It should extend below the body sill and contact the wear plate bolted to th
46. nt Rie thee NS e E E E 13 lure M 13 Welding EQUIPME Mt 14 jag eemper H 15 Dissimilar cci cmt H 15 Driveshaft EXtenSiO DN o oem 16 Driveshaft Extension DS SII n TT c aiaei 16 Two Piece Driveshaft Bearings bk act se ubequi ie daxskassud aka Fuit ERU TENE osi RUM ER SR EMEN CE M UD M UNA SM 17 Universal Joint AnGles and PhaSiNg vC 18 Multiple Piece Driveshaft Alignment Procedure ccciciicssccctevieisecctacectssicenteciivenestanecussaetanaiuad snedeeesneabassaestarusvandansdariiniadancadercieansbions 19 continued on next page Chassis Best Practices 2010 Index cont d BODY eB pp cm ned ei eee ane nn nee 20 General PR gM Nee OM eae cect eed ccc cedar decree 20 Body Mo nting Considerations cmn 21 Body Equipim eit Attachment OS cru Dun Pus nu
47. nt is met e Crossmembers should be rigidly welded bolted or riveted to the frame rails Designed to avoid retention and other foreign matter Should not protrude excessively below the underbody and frame rails to prevent reduction in ramp break over and ground clearances FLRNGE NOTCH SECTION FRTIGUE MODULUS STRENGTH FLRNGE 19 TO 30110 TO 65 FLRNGE HOLE HOLE FLRNGE 13 NOTCH WEB NO LOSS Loss RADI 6 88 MM 0 275 IN Figure 10 continued on next page Chassis Best Practices 2010 Ey Uri INTEGRATION CHASSIS BEST PRACTICES Extending Wheelbase Moving Axle cont d Analyzing Frame Failure Causes In some cases such as a vehicle collision the reason for frame failure is easily apparent In others however determining the cause is considerably more difficult Frame failures can generally be traced to one of three reasons e Vehicle collision Excessive bending moment Localized stress concentration Collisions Failures caused by collisions should be repaired using proper methods and reinforcements as necessary Excessive Bending Moment Overload improper weight distribution or vehicle misapplication can Cause excessive bending moment failures This type of failure occurs at different areas on different types of vehicles Localized Stress Concentration Localized stress concentration failures may result from bending moment stresses However stres
48. ortion of the frame unless the area to be covered is closer FRAME INSERT 152 0 MM 6 IN OVERHRNG FRAME H UN than 305 mm 12 in from any exhaust component For eo ee A Pme el 19 0 MM 75 IN components falling within this area use paint rather than 89 9 MM 3 5 IN iio undercoating to provide corrosion protection 25 0 Extending The Frame Rear Overhang eT ee When lengthening rear frame extensions SVMs must exercise great LOCATE APPROX aes i id ad ly affecting vehicle performance in th REINFORCEMENT 1520 HH GOIN caution to avoid adversely affecting vehicle performance in the CLEARANCE HOLES FILLET RADIUS TO following areas WELD TO FRAME INSERT ALLOW GAP E e Excessive rear extensions allow customer opportunity to Figure 8 significantly unload the front end of the vehicle This can result in customer dissatisfaction with vehicle braking and or steering Secure the L shaped reinforcement with clamps to the outside of the frame rail There should be no visible gaps between the frame rail and the reinforcement other than at the bend Fillet weld the and handling Rear frame extensions must be long enough to protect vulnerable reinforcement to the frame rail using a skip weld technique That is a pas D ue E ps is PM d 9 b 50 8 mm 2 in weld followed by an equal space continuously along etie d US the span of the reinforcement For guidelines on frame wax
49. rds or amendments issued by the Environmental Protection Agency appear in the Federal Register from time to time You may obtain the Federal Register through the Superintendent of Documents U S Government Building Office Washington D C 20402 Various state and local requirements regulate vehicles above and below 10k GVWR For specific rules test procedures and permissible noise levels refer to specific state regulations Exhaust pipe modifications must comply with recently enacted federal EPA regulations regarding exhaust system leaks Refer to federal regulations for additional information Exhaust System Design When designing specialty vehicle exhaust systems SVMs should observe the general recommendations listed below e Make sure that the design maintains proper design and spacing of the OEM hanger bracket sufficient clearance for thermal expansion of materials e Use only aluminized 409 stainless steel or aluminized mild steel to lengthen exhaust pipes e To avoid excessive exhaust back pressure and resultant loss of engine power make sure the exhaust pipe has smooth bends and no sharp edges to impede exhaust flow continued on next page CHASSIS Best PRACTICES Exhaust System cont d Exhaust System Design cont d The exhaust system rotates with the engine This requires a e Under extreme operating conditions exhaust temperatures minimum clearance of 17 mm 0 7 in from the floorp
50. s levels would not be high enough to cause any difficulty without localized stress concentration points Localized stress concentration points maybe caused by poor body or fifth wheel mountings special equipment or accessory installation improper welding or welding methods improper reinforcements loose bolts or rivets defective material They may also result from high bending loads coupled with severe torsional loads e g off road applications Chassis Best Practices 2010 Fifth Wheel Installation General Motors recommends attaching fifth wheel or body mounting to the frame rail web section not through flanges Refer to the GM Body Builders Manual for proper installation procedures Using U bolts to attach fifth wheels or bodies is not an approved installation method Doing so may result in the development of high stress concentration Special Equipment Accessory Installation Installing special equipment or accessories can cause high stress concentrations due to the attachment method or their added weight Never drill holes through flanges Avoid drastic changes to section modulus Section modulus changes usually occur when large mounting plates are added to support special equipment Avoid mounting heavy equipment across the flanges or on side rail webs Doing so may result in stress concentration high enough to cause failure of the nearest crossmember bracket or other frame stiffener or
51. s operative Do not add suspension accessories or make any modification that will change axle loads or trim height Such changes may provide a false reading to the brake proportioning valve Vehicle weight weight distribution and center of gravity determine the appropriate proportioning valve continued on next page CHASSIS BEST PRACTICES Brakes cont d Brake Lines Allow at least 17 mm 0 7 in clearance between brake lines and moving components and at least 13 mm 0 5 in between brake lines and vibrating components Clip brake lines at least every 762 mm 80 in Figure 31 shows proper brake line routing and fastening Cover all brake line extensions with a protective coating to prevent corrosion use GM specification 123m or equivalent Construct brake line extensions of steel tubing capable of withstanding operating pressure of at least 2 500 PSI Route brake lines along inner frame sections being careful Do not repair kinked or cracked brake lines Replace all to avoid sharp edges protruding objects and short bends damaged lines with new brake lines There must be no evidence of brake line twist Do not splice brake lines Replace entire brake line at required length REAR AXLE ASSEMELY Figure 31 next Chassis Best Practices 2010 co ned ona page POTETE INTEGRATION CHASSIS BEST PRACTICES Brakes cont d Additional recommendations
52. se that may occur during welding Doing so may cause system damage After modification use a fuel system prime tool to activate the fuel pump Cranking the engine to prime the fuel system creates a heavy drain on the battery Chassis Best Practices 2010 All engines require a fuel return system which returns excess fuel from the injection pump and injector nozzles back to fuel tanks Care should be taken that these lines are not blocked nor their hoses pinched The engine may run poorly or stall if these lines are restricted or blocked All gasoline engine vehicles are equipped with fuel evaporative emission control equipment which is certified to be in compliance with the Federal or applicable California Vehicle Emission Standards Alterations to fuel tank and metering unit lines canister or canisters canister filters canister purge control valves relay switches tank auxiliary vent valve engine speed controller or other devices systems are therefore not allowable since vehicle adherence to C A R B and Federal regulations may be affected Diesel powered vehicles incorporate water drain provisions in the fuel system These valves are only to be opened when removing water and contaminants from the fuel system FRAME ASM HOSES PIPE ASM o 2 857 SENDER ASM gt E P MEE d S RT 2 9 TANK ASM Sy PIPE ASM 2 Bz Soy HOSES PIPE F BOLT SCREW CLIP PIPE RSH FRT
53. st corrosion protection Before beginning any welding EE operation locally remove the wax using one of the 5 Attach a cutting fixture rest to the frame for increased cutting accuracy following methods 6 Medium Duty vehicle with l beam front axles Use the The following steps are recommended as preparations for altering the wheelbase Steam e correct tie rod arms when significant shortening or Hot water at approximately 500 PSI lengthening is planned Consult the General Motors Parts Scrape and then use mineral spirits to wipe off Catalog for the proper selection any remaining wax VERTICRL REFERENCE MARKS CUT LINE HORI ZONTAL REFERENCE WORK 1 2 WEB HEIGHT APPROXIMATELY 76 2 101 6 3 4 0 IN BOTH SIDES Figure 2 continued on next page Chassis Best Practices 2010 MvR CHASSIS BEST PRACTICES INTEGRATION Extending Wheelbase Moving Axle cont d Frame Splice Procedure 3 Chamfer the outside edge of both the frame and the insert at a 30 degree angle leaving 1 2 of the thickness Figure 3 1 Locate a specific frame splice cut location observing the 4 Relocate rear frame section of the vehicle to install frame insert location guidelines already outlined Cut the frame within the when lengthening frame splice zone 5 Fixture and clamp the insert to ensure correct alignment Figure 4 Make dimensional checks against predetermined reference marks
54. te electrical wires fuel lines or HVAC hoses over the exhaust system Shielding Heat shields are necessary in areas where high exhaust temper atures will affect vehicle component performance Heat shields should be made of aluminized steel with a minimum 0 9 mm 0 035 in thickness Do not alter or remove any heat or grass shields from the OEM exhaust system Also provide similar shielding to any exhaust component extension If exhaust pipes are extended rearward directly past the spare tire install shielding to protect the tire Mount heat shields to the underbody and or exhaust system components catalytic converter and muffler Some vehicles may also require shields for the propshaft hanger bearings Undercoating Do not apply undercoating to e Any part of the exhaust system e Any component within 300 mm 11 8 in of the exhaust system Figure 34 Chassis Best Practices 2010 CHASSIS BEST PRACTICES INTEGRATION Suspension System Suspension System C K Models are designed so that camber and caster do General Requirements not need adjustment unless severe road impact or accident SVMs should adhere to the following recommendations ina ANENE is completed and while at normal operating load with trim Do not weld to any axle assembly height as specified e Design body and equipment arrangements that allow proper load distribution on both front and rear a
55. the tires so that the rear suspension is at curb height 3 Attach one end of a string from the center of the transmission spline as indicated to the center of the pinion attachment flange Pull string taut 4 Measure the vertical distance from the center of the bearing mounting area of the crossmember to the string dimension H Figure 19 5 With a square just contacting the string in the lateral directions mark the crossmember to indicate the correct lateral position of the center of the bearing 6 Add shims under the bearing so that the center height of the bearing is equal to the measurement taken in step 5 Mark the base of the bearing to indicate its lateral center 7 Remove string Install bearing and driveshaft with shims under the bearing so that its center aligns laterally with the mark on the crossmember The bearing center should be at the same point as the string For vehicles requiring more than one bearing support perform this procedure for each bearing uis BREAKING SUPPORT CROSSMEMBER STRING METHOD Figure 19 Chassis Best Practices 2010 continued on next page CHASSIS Best PRACTICES Body Mounting Optimum body mount location varies by frame wheelbase Ambulance and other sensitive cargo bodies require reduced length The best locations for effective isolation from road stress on the body and frame To accomplish this minimize vibration are those closest to frame crossmembers an
56. ty and performance while minimizing cost and part assembly complexity General Motors has conducted extensive engineering analysis of the frame with the objective of replicating base frame thickness for optimum dynamic performance This analysis is the basis for recommendations on frame construction sections section modules metal thickness and specifications The frame extension must overlap the existing frame to ensure adequate strength in the tie in areas These areas are vehicle stress risers subject to significant loads even during normal vehicle use SVMs therefore should make every attempt to ensure consistent installation in the tie in areas Alterations When modifying the wheelbase SVMs assume full responsibility for compliance with applicable motor vehicle safety standards e warranty on items such as driveshafts universal joints center bearings and rear transmission tailshaft transfer case and transmission case fractures output shaft bushings bearings brakes fuel systems and any other related component failures Additionally the modifier s owner manual must alert the customer that parts for the reworked area s are not available through the General Motors service parts system Chassis Best Practices 2010 Frame The SVM is responsible for any alterations to the frame assembly including hole drilling welding and modifications of any type The SVM must also assume complete responsibility for relia
57. veshaft the front must align with the rear shaft in both side and plan views Figure 17 Check for this vertically and along the horizontal center Recommended bearing locations vary with vehicle stretch length If line Figure 18 the driveshaft exceeds 1 524 mm 60 in use a two piece assembly with an in line bearing assembly Keep the driveshaft lengths as close to equal as possible DRIVESHRFT SUPPORT BERRING Figure 16 CORRECT PHASING YOKE LUGS EARS ALIGNED INCORRECT PHASING YOKE LUGS EARS NOT ALIGNED Figure 17 continued on next page Chassis Best Practices 2010 Extending Wheelbase Moving Axle cont d IN LINE BEARING ASSEMBLY Jj CHECK Figure 18 For maximum support mount bearing assembly to a cross member Final driveshaft alignment must allow vertical and horizontal bearing adjustment Make sure to protect the in line bearing from common operating conditions such as weather and road debris General Motors recommends mounting a protective bridge between the bearing assembly and the ground Fasten the bridge with bolts to facilitate serviceability Splicing driveshaft tubes is not recommended Splice welds create irregularities on inner and outer surfaces making it difficult to balance the driveshaft Additionally splice welding may cause embrittlement increasing the possibility of driveshaft failure Protect the driveshaft and universal joints from common operati
58. xles Use designs that consider and maintain lateral load equalization Make sure that the unladen vehicle s center of gravity after conversion falls within the limits specified in the FMVSS 105 section of the Incomplete Vehicle Document Do not route pipes wiring or related components in suspension component paths of motion These Axle in full rebound components include rear axle springs shocks brake Allow the following clearance for tire chains pipes and hoses Rear Suspension Clearance Provide clearance to the body for the suspension axle and tires under the following conditions Axle in full jounce against the metal to metal stop Axle at 4 5 degree roll Axle at design position Design for maximum growth tire Front Suspension Allow 42 mm 1 66 in to sides of tire e Since there is a large variation in completed vehicle front Allow 64 mm 2 5 in to top of tire weight due to differences in body weight and equipment the front suspension alignment must be checked and reset after the vehicle is completed Caster and camber should be set with reference to the A dimensions On C3500 Refer to the GM Body Builders Manual C K section for trucks with I beams camber and caster are designed into additional information on clearance to body chassis and the axle suspension and cannot be adjusted rar SuUSpensIon See the Service Manual for complete alignment proce
59. y mounting applications NTEA Recommended Body Mounting Practices The National Truck Equipment Association NTEA advises that proper body mounting practices and materials are necessary in order to avoid damaging the frame side rail and body This can occur when load and chassis movement Cause uneven distribution of stress and strain Attention to proper mounting and specifications is also critical to maintaining vehicle ride and handling characteristics The NTEA Body Practices Subcommittee has reviewed the mounting methods of several chassis manufacturers and has identified four general types Type 1 U Bolt Threaded Rod and End Plate This mounting method uses U bolt threaded rod and end plate to secure the body s longitudinal mounting rails to the chassis frame Fillers or strips of hardwood or hard rubber act as cushions between the longitudinal mounting rails and the chassis frame Secure the filler to frame or rail with steel banding or equivalent The hardwood filler should taper approximately 1 inch per foot starting at the front end and extending about 300 mm 11 8 in back The first tie down should be positioned no more forward than the rear edge of the taper For longitudinal body control secure the shear plates with grade 8 bolts or weld them to the longitudinal mounting rails Prevailing torque nuts are preferred in all threaded connections over double nuts Spacers prefer ably metal placed between the flanges of bot
Download Pdf Manuals
Related Search