GMC G VAN User manual

G Van (GMT 600) 2002
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BODY BUILDERS INSTRUCTIONS .......................................................................................................................................................... 1
Section 0 – General Instructions ..................................................................................................................................................... 1
Welding ....................................................................................................................................................................................... 2
Labels ......................................................................................................................................................................................... 2
Section 1 – Body................................................................................................................................................................................ 3
Conversions ................................................................................................................................................................................ 3
Air Conditioning .......................................................................................................................................................................... 4
Rear Air Conditioning .................................................................................................................................................................. 4
Section 2 – Frame ............................................................................................................................................................................. 5
Flanges ....................................................................................................................................................................................... 5
Holes ........................................................................................................................................................................................... 5
Alterations ................................................................................................................................................................................... 6
Shear Plate Attachments ............................................................................................................................................................ 6
Trailer Towing .............................................................................................................................................................................. 6
Section 3 – Front Suspension .......................................................................................................................................................... 7
Section 4 – Rear Suspension ........................................................................................................................................................... 7
Section 5 – Brakes ............................................................................................................................................................................ 8
Section 6 – Engine............................................................................................................................................................................. 9
Section 7 – Transmission................................................................................................................................................................ 11
Section 8 – Fuel and Exhaust ......................................................................................................................................................... 11
Fuel Systems ............................................................................................................................................................................ 11
Fuel Fill ...................................................................................................................................................................................... 12
Fuel Lines .................................................................................................................................................................................. 12
Fuel Tank ................................................................................................................................................................................... 13
Gaseous Fuel Conversions ....................................................................................................................................................... 14
Exhaust System ........................................................................................................................................................................ 14
Section 9 – Steering ........................................................................................................................................................................ 15

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BODY BUILDERS INSTRUCTIONS – Continued
Section 10 – Tires ............................................................................................................................................................................ 16
Section 12 – Electrical Battery and Battery Cables ..................................................................................................................... 16
Battery Installation .................................................................................................................................................................... 17
Accessory Power Supply Feeds ............................................................................................................................................... 19
Section 13 – Cooling ....................................................................................................................................................................... 20
CHASSIS
General Arrangement – G (114/214/217/314/317)(05/06) ............................................................................................................. 21
BODY
135” Wheelbase, Exterior, 5, 8 or 12 Passenger – G (114/214/314)(05/06) ................................................................................. 22
135” Wheelbase, Interior, 5, 8 or 12 Passenger – G (114/214/314)(05/06) .................................................................................. 23
155” Wheelbase, Exterior – G (217/317)(05/06)............................................................................................................................. 24
155” Wheelbase, Interior, 5, 8 or 12 Passenger – G (217/317)(05/06) ......................................................................................... 25
155” Wheelbase, Interior, 15 Passenger – G (217/317)(05/06) ..................................................................................................... 26
Seat Riser Assembly Mounting – G00000 ..................................................................................................................................... 27
Side Stringer Locations – G (114/214/217/314/317)(05/06) ......................................................................................................... 28
Roof Bow Locations – G (114/214/217/314/317)(05/06) ............................................................................................................... 29
Exterior Glass – G (114/214/217/314/317)(05/06).......................................................................................................................... 30
Sign Area – G (114/214/217/314/317)(05/06) ................................................................................................................................. 31
Cutaway, Exterior – G (315/318/319)(03/32) .................................................................................................................................. 32
Cutaway, Interior – G (315/318/319)(03/32) ................................................................................................................................... 33
G Cutaway, Rear Flange ................................................................................................................................................................. 34
FRAME
Light Duty Crossmember Arrangement, 135” Wheelbase – G (114/214)(05/06) ........................................................................ 35
Heavy Duty Crossmember Arrangement, 135” Wheelbase – G (214/314)(05/06) ...................................................................... 36
Light Duty Crossmember Assembly, 155” Wheelbase – G 217 (05/06) ...................................................................................... 37

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FRAME – Continued
Heavy Duty Crossmember Arrangement, 155” Wheelbase – G (217/317)(05/06) ...................................................................... 38
Heavy Duty Cutaway Crossmember Arrangement, W/Soft Mt loc & Park Brake routing – G 315 (03/32) .............................. 39
Heavy Duty Cutaway Crossmember Arrangement, W/Soft Mt loc & Park Brake routing – G 318 (03/32) .............................. 40
Heavy Duty Cutaway Crossmember Arrangement, W/Soft Mt loc & Park Brake routing – G 319 (03/32) .............................. 41
Spare Tire Carrier – G (114/214/217/314/317)(05/06) ................................................................................................................... 42
Trailer Hitch, 135”/155” Wheelbase – G (114/214/217/314/317)(05/06) ...................................................................................... 43
AXLE/SUSPENSION
Front Axle/Tire Data Chart – G (114/214/217/314/317)(05/06)..................................................................................................... 44
Rear Axle/Tire Data Chart – G (114/214/217/314/317)(05/06)...................................................................................................... 45
Front Axle/Tire Data Chart – G (315/318/319)(03/32) ................................................................................................................... 46
Rear Axle/Tire Data Chart – G (315/318/319)(03/32) .................................................................................................................... 47
FUEL TANK
General Arrangement, Fuel, 135”/155” Wheelbase – G (114/214/217/314/317)(05/06) ............................................................. 48
General Arrangement, 35 Gallon and 55 Gallon – G (315/318/319)(03/32) ................................................................................. 49
EXHAUST
Muffler Arrangement, 135”/155” Wheelbase – G (114/214/217/314/317)(05/06)........................................................................ 50
Light Duty Converter Assembly, Engine Options L30, L31, L35 – G (114/214/217/314/317)(05/06) ......................................... 51
Heavy Duty Converter Assembly, Engine Options L31 California, L35 – G (217/317)(05/06).................................................... 52
Heavy Duty Converter Assembly, Engine Options L31, L18 – G (217/317)(05/06) ..................................................................... 53
Heavy Duty Converter Assembly, Engine Option L65 – G (217/317)(05/06) ............................................................................... 54
Heavy Duty Cutaway Converter/Muffler Assembly, Engine Options L35 – G 31503 ................................................................. 55
Heavy Duty Cutaway Converter/Muffler Assembly, Engine Options L18, L31 – G 315 (03/32) ................................................ 56
Heavy Duty Cutaway Converter/Muffler Assembly, Engine Options L18, L31 – G 317 (03/32) ................................................ 57
Heavy Duty Cutaway Converter/Muffler Assembly, Engine Options L18, L31 – G 319 (03/32) ................................................ 58
Heavy Duty Cutaway Converter/Muffler Assembly, Engine Option L65 – G (315/318/319)(03/32) .......................................... 59

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BODY BUILDERS INSTRUCTIONS
The Incomplete Vehicle Document (IVD) is supplied with each incomplete vehicle, and provides information that should be used by
intermediate and final stage manufacturers in determining conformity to applicable Federal Motor Vehicle Safety Standards (FMVSS).
The IVD also includes information which must be followed in order to ensure that Environmental Protection Agency (EPA) and California
emissions certification requirements and NHTSA Fuel Regulations are met.
The Body Builders Book contains information that may be used in addition to the IVD for any manufacturer making alterations to a GM
complete/incomplete vehicle. No alteration should be made to the incomplete vehicle which either directly or indirectly results in any
component, assembly or system being in nonconformance with any applicable Federal Motor Vehicle Safety Standard or Emission
Regulation. Intermediate and final stage manufacturers should be familiar with all Federal Motor Vehicle Safety Standards and Emission
Regulations and aware of their specific responsibilities as manufacturers.
For further assistance contact Upfitter Integration at: 1 [phone], or go to our Web site at “http://www.gmupfitter.com.”
Section 0 — General Instructions
Check for proper clearance between body members and chassis components, which may in any way affect the reliability and
performance of the vehicle by developing abrasion and wear points from moving parts or degradation from extreme environment or
thermal exposure or may increase interior noise. Any attachments must consider chassis components for jounce and rebound motion at
maximum GVW.
Check headlamp aim and all vehicle illumination systems for proper operation when the vehicle has been completed. Re-aim headlamps
when necessary. Check for proper operation of windshield washer, wipers and defroster system. In no case should any alterations affect
the function, physical or mechanical properties, environment or vital spatial clearances of the components, assemblies or systems.
Extreme care must be taken when working on vehicles which have been equipped with Powertrain Control Module (PCM), Sensing and
Diagnostic Module (SDM) (Air Bag Control Module) and ABS Control.
Do not mount any components with large magnets, such as stereo speakers, in the area of the driver’s seat due to the Sensing and
Diagnostic Module (SDM).
The Sensing and Diagnostic Module (SDM) located under the driver seat and S. I. R. sensor at the lower radiator support cannot, under
any circumstance, be moved from their present mounting locations.
(Section 0 — continued on next page)

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(Section 0 — continued from previous page)
Welding
CAUTION: Fuel tank and fuel lines must be drained and all vapors purged to ensure non-combustible mixture before any welding,
brazing or soldering.
If arc-welding is employed on the chassis or body parts or components which could be damaged by welding temperatures, these parts
must be removed or adequately shielded. Some examples are brake lines, fuel lines and fuel tank assembly, electrical wiring, electronic
modules, sensing and diagnostic module under the drivers seat and S.I.R. sensor under radiator support. To avoid electronic component
damage, disconnect battery (batteries); disconnect the negative cable first, followed by the positive. To reconnect cables; connect the
positive first, then the negative.
When welding low carbon steel side rails, crossmembers and brackets, emphasis is placed upon weld application techniques to avoid
stress risers that may adversely affect frame operating stresses. Note that some of the frame sections are made of high-strength-low-
alloy steel that could be adversely affected by heating due to welding. Also, prior to welding, the area to be welded and surrounding area
must be cleaned of all frame protective coating.
After welding, when parts are cool, carefully inspect wiring and electrical components for shorts or other damage which could draw
excessive currents and possibly cause an electrical system short when the battery is reconnected. Also, assure that the fuel systems and
especially the fuel lines are not damaged or distorted from the welding heat. Apply protective coating to areas where coating was
removed.
Service and service replacement parts for your add-on systems may not be available from a GM dealer. Those installing aftermarket
systems should provide information as to where and how to obtain service.
Labels
All labels on the vehicle (any message applied to the
vehicle or vehicle component that informs, instructs, or
warns) must appear on the completed vehicle so the user
can read them easily and without obstruction.
NOTE: In order to be in compliance with FMVSS 208, no
other label shall be installed on the same side of
the sunvisor as the Inflatable Restraint Caution
(Air Bag) Label.

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Section 1 — Body
Accessory items such as refrigerator, hot water heater, furnace, etc., which operate on liquid propane gas should be located and
protected to prevent exposure to any flame.
Body structures, interior and accessory arrangements must be designed into the vehicle to provide for proper load distribution on both
axles and not to exceed any gross axle weight ratings. Lateral load equalization must also be maintained. The resultant Center of Gravity
of the unladen vehicle must be within the limits tabulated in the FMVSS 105 section of the Incomplete Vehicle Document.
Body insulation provided by General Motors should not be removed. This includes any thermal or underbody heat shields. This insulation
is provided to protect the vehicle body and occupants from excessive heat and/or provide noise attenuation. Any replacement material
internal to the occupant compartment may have to be certified for MVSS 302 standard on flammability. Some areas of specific interest
are:
• Underbody exhaust, muffler and tail pipe shields and insulators.
• Rear load floor interior insulation.
• Front floor interior insulation.
• Dash mat insulation.
• Engine cowl insulation - interior and exterior.
• Engine cover insulation.
Conversions
Conversions which remove the roof bow above the front doors must provide equivalent tie-in between door pillars.
A minimum of 10º departure angle should be maintained if frame and/or body is extended.
If body builder installs seating other than that supplied with vehicle, it is the body builder’s responsibility to ensure that the seating and
restraint systems comply with FMVSS requirements. The restraint systems supplied with the vehicle were designed to accommodate the
seating reference points and seat travel of the original equipment seats only.
(Section 1 — continued on next page)

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(Section 1 — continued from previous page)
Air Conditioning
For additional information refer to Engine - Section 6.
NOTE: Air conditioning systems using R-134A refrigerant are equipped with metric fittings to prevent interchange with R-12 refrigerant
components. Do not interchange R-134A components, refrigerant oil or service equipment with R-12 components, refrigerant oil
or service equipment.
Rear Air Conditioning
The A/C and heater lines are usually routed between the vehicle floor and the exhaust system heat shields. The electrical connectors for
the rear HVAC are usually routed on the inside right rear pillar and it also has a switch on the front dash to control the rear air.
NOTE: It is imperative that the design of the HVAC lines and materials selected by the Conversion Companies, upfitter (or HVAC supplier)
provide mechanical attachments to the vehicle to protect against abrasion, engine roll, and vibration. The lines must also be
insulated to protect against engine or exhaust system heat. Please be aware that an improperly installed HVAC system by the
SVM may damage OEM and/or van conversion system components.
This unit may be equipped with A/C quick-connect fittings on the liquid tube (high pressure) and the suction (low pressure) return tube.
These fittings are designed to accept matching Aeroquip connecting fittings attached to pre-charged lines. This allows a one time only
connection to the O.E.M. charged A/C system without having to discharge, evacuate and recharge for the connection of a rear A/C
system. These quick connects must be used for warranty coverage of the A/C system.
A modification to the A/C system which causes the A/C plumbing lines to increase in length (such as the addition of a rear after-market
evaporator and blower assembly) will necessitate the following changes:
• Lubrication – PAG refrigerant oil must be added to rear system to provide lubrication for compressor. Refer to the G Van Service
Manual for specifications.
• Refrigerant – Add R-134A refrigerant to system based on sizing of new tubes, hoses and evaporator. Contact your A/C supplier
for recommended charge.
• Label – Revise/modify GM charge label (located on the front face of evaporator) from factory recommended charge for a front
system only to body builder’s new recommended dual system per SAE J639. This is important for servicing the A/C system so
that the technician knows the correct amount to add to the modified system.
• Heater/Defroster – No modifications should be made to the heater/defroster system or coolant supply which could affect
compliance to FMVSS 103.

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Section 2 — Frame
Hole drilling, welding, modifications, or alterations to the frame assembly are the responsibility of persons performing these operations.
These same individuals assume complete responsibility for frame assembly, reliability, performance after alterations and compliance to
applicable FMVSS requirements.
The following procedures and specific precautionary instructions are recommended for proper installation of special bodies and/or
equipment on GM frames. Failure to follow these recommendations could result in serious damage to the basic vehicle.
New soft mount provisions for RV and Commercial bodies (vehicles 03/32 YFI). Locations found on the reference pages 38 - 40 in the
Body Builders Manual.
Flanges
Do not drill holes in frame flanges:
• Within 20 mm (0.75 in.) of radius tangent and 25 mm (1.0 in.) of raw edge.
• Larger than 12 mm (0.50 in.).
• Closer to each other than twice the hole diameter.
NOTE: The frame flanges holes recommendations might be affected by the soft mount provisions/locations.
Holes
Holes to mount brackets, supports, and out-riggers must be drilled in the vertical side web with the following restrictions:
• Material between edge of hole and inside of upper or lower flange must not be less than 37 mm (1.50 in.) for low carbon steel
(36,000 PSI yield).
• The minimum edge distance between any two (2) holes must be larger than twice the diameter of the larger hole.
• No holes should exceed 20 mm (0.75 in.) in diameter.
• All holes should be drilled in the frame using appropriate drilling practice and safety precautions.
(Section 2 — continued on next page)

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(Section 2 — continued from previous page)
Alterations
If the wheelbase is modified, the alterer must take responsibility for compliance with affected motor vehicle safety and emission
standards and for 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 customer must be alerted in the modifier’s owner’s manual that parts for the reworked area are not available through the
General Motors Service Parts System.
Shear Plate Attachments
Attachments of shear plates should be accomplished by using existing manufacturing holes already available.
When additional holes are required for shear plate attachment, they should be no larger than 20 mm (0.75 in.) in diameter. Holes are to be
drilled no closer than 63.5 mm (2.5 in.) apart. For holes drilled forward of the rear axle, centers are to be no closer than 63.5 mm (2.5 in.)
from the top or bottom flanges and no closer than 89 mm (3.5 in.) from any suspension attachments. For frame holes drilled rearward of
the rear spring hanger bracket, hole centers are to be no closer than 51 mm (2.0 in.) from the top or bottom flange and no closer than 89
mm (3.5 in.) from suspension attachments.
Required large holes such as 20 mm (75 in.) diameter or larger, should be kept to a minimum required opening. Tubes should be welded
in place if holes in excess of 25 mm (1.0 in.) diameter are required.
Trailer Towing
The Incomplete Vehicle Document specifies that the CG location be within certain limits. The Body Builder must use all appropriate data.
Note to Body Builder/Final Stage Manufacturer: Failure to keep body and payload CG at least 26 inches forward of centerline of rear
axle will result in degradation of trailer towing capacity. Consult the Trailer Towing Guide to determine maximum tongue load for your
vehicle.

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Section 3 — Front Suspension
See chassis data information for clearances and assistance in calculating trim heights.
Since there is a large variation in completed vehicle front weight due to differences in body weight and equipment, care must be taken not
to exceed the GAWR/GVWR. Also, the front suspension alignment must be checked and reset if necessary after the vehicle is completed.
Caster and camber should be set with reference to the “A” dimensions.
See The G Van Service Manual for complete alignment procedure, specifications and measurement of the “A” dimension under
“Diagnosis and Front Alignment” section.
Section 4 — Rear Suspension
Due to differences in body weight and equipment, care must be taken not to exceed the GAWR/GVWR.
Clearance to body should be provided for the suspension, axle, driveshaft and tires under the following conditions: (1) Axle in full jounce
against the metal-to-metal stop, (2) Axle at 4.5º roll with one side of axle in full jounce at the metal-to-metal stop and (3) Axle at design
position. Allowance for the tire chain clearance shown on a maximum grown tire must allow for (1.66 in.) clearance to the sides of the tire
and (2.5 in.) to the top of the tire. Be sure sufficient clearance is provided for suspension, axle, and tire and wheel through full vertical
travel (up and down).
Pipes, wiring, conduits and any other related components must not be placed where they cross the path of motion of 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.
NOTE: Notification to the consumer may be required in certain states if tire chains cannot be used.
See chassis data information for additional clearances and for assistance in calculating trim heights.

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Section 5 — Brakes
See The G Van Service Manual for brake specifications.
Due to the critical nature of brake systems, anyone making modifications or alterations must assume complete responsibility for system
reliability, performance and certification to FMVSS 105.
All G10 and some G20 models are equipped with front air dams below the front bumper as shown in the illustration. These air dams are
equipped with brake cooling openings as shown. These openings should not be obstructed by the addition of any accessories that would
impede the flow of air to the front brakes.
It is mandatory that no change be made to the brake master cylinder location, brake pedal push rod length or pedal position.
Ensure that the hydraulic brake system is free of air and hydraulic leaks. Bleed brakes if required, following procedures as outlined in the
G Van Service Manual. Ensure that the vacuum booster system or hydraulic booster system is functional and free of leaks.
Check master cylinder fluid level and fill as necessary. Use only DOT3 Fluid from a sealed container. Delco Supreme 11 is recommended.
(Refer to Owner’s Manual).
Check power steering fluid level for models equipped with hydraulic booster brake. (Refer to Owner’s Manual).
Added floor covering or carpeting must not restrict service or parking brake pedal travel from released position to full pedal travel.
(Section 5 — continued on next page)

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(Section 5 — continued from previous page)
No body part or chassis-mounted component may be located within 2.0 in. of brake hose routing in all wheel and axle positions. All
exhaust system components must also have a minimum of 2.0 in. clearance to brake hoses in closest positions. (Be sure to account for
brake hose travel with suspension.) Note: Heat shielding is likely required with clearances even greater than 2.0 in. Keep the brake fluid
temperature below the boiling point of water under all operating conditions.
Body builder is to verify that the brake warning switches are operative. (The brake warning switch on models equipped with vacuum-
hydraulic brakes is located adjacent to the master cylinder vacuum unit.) This includes the brake system differential pressure. (The
parking brake actuator switch is mounted on the park brake apply mechanism which is mounted on the L.H. body side inner under the
instrument panel.)
The park brake system is equipped with an automatic adjuster. Do not separate the park brake cables unless the apply mechanism
is blocked out. The adjuster will wind in the cable until it can no longer be reconnected if not blocked (pinned). See the Pin UP procedure
outlined in Section 5, Enabling the Park Brake Automatic Adjuster, in the G Van Service Manual.
Section 6 — Engine
For additional information refer to Body - Section 1.
Air conditioning and auxiliary belt-driven equipment installation recommendations:
No alterations or additions to the accessory drive belt system will be warranted on either multiple belt systems or serpentine belt
systems.
The serpentine belt type of drive is designed as a total system, incorporating a single poly-V belt and an automatic tensioner. In this type
of system, degrees of pulley wrap, belt tension, and pulley alignment are very critical factors. Modification is not recommended.
The fan and fan clutch that come with the vehicles are matched to the equipment and conditions encountered in normal operation.
Substitution of the fan and/or fan clutch may affect cooling performance. A substitute fan may be subjected to excessive stresses and
might break. Substitution is therefore not allowed.
The incorporation of an aftermarket air conditioning system could have the following consequences:
• Vehicle/engine/coolant overheating in certain geographical areas that normally experience high ambient temperatures.
• Restrictions to engine cooling fan airflow resulting in higher fan blade stress.
(Section 6 — continued on next page)

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(Section 6 — continued from previous page)
• Inadequate air conditioning performance unless system capacity is enough to cool the interior space of the completed vehicle.
Due to the critical nature of the accelerator system, anyone making modifications or alterations assumes complete responsibility for
system reliability, performance and compliance to FMVSS 124. Caution must be exercised so that the accelerator cable routing is
unchanged.
• Do not use accelerator cable or clips to route wires, harnesses or other cables. Cable sheath must be clipped so as not to pinch
inner cable. Cable must not be loose in clip allowing sheath to move when accelerator pedal is applied and released.
• Cable must not be subjected to kinking or routing across any sharp edges.
• Cable routing must be perpendicular to the surface of the front-of-dash at the dash fitting. No objects or routings should force
cable to have a bend at the dash fitting. Flexible components (hoses, wires, conduits, etc.) must not be routed within 2.0 in. (50
mm) of moving parts or accelerator linkage unless routing is positively controlled.
• Caution must be taken so that the accelerator pedal mounting and location remains unchanged. Guidelines for accelerator
pedal locations are as follows:
a. Ensure that the accelerator can freely operate from idle to wide-open throttle position and return. Make sure that the pedal
will not hang up on any nearby items such as carpets, floor, screws, wiring harnesses, etc. Engine cover should have at
least one inch (25 mm) clearance to side of accelerator pedal with the carpet mat installed.
b. Accelerator to brake pedal relationship has been designed to provide minimum driver movement and should not be
altered in any way.
The gasoline engine induction and/or ignition system is certified in compliance with the Federal Vehicle Emission Standards. Any
alterations to the systems or components could void compliance and render the vehicle illegal. Systems include:
• Fuel system - Port Fuel Injection and associated tubes, hoses and pipes, air cleaner, outside air hose and spacer heat stove
and heat stove pipe, fuel pump and inlet manifold, fuel vapor canister.
• Exhaust system.
• Ignition system distributor and initial spark timing setting, spark plugs and spark plug wires.
• Crankcase ventilation system.
The diesel engine induction and injector pump system is certified to be in compliance with the Federal Vehicle Emission
Standards and/or Noise Standards. Any alterations to the system or components could void compliance and render the vehicle illegal.
(Section 6 — continued on next page)

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(Section 6 — continued from previous page)
Systems include:
• Fuel system - Injection pump, injector lines and injectors, fuel return hoses and pipes, air cleaner, outside air hose, fuel pump,
fuel filter, fuel heater assembly and intake manifold.
• Exhaust system.
• Crankcase pressure regulation system.
External engine components such as air cleaner, crankcase pressure regulator valve, alternator, injection pipes, fuel return hoses from
injectors, exhaust manifolds, oil fill pipe, etc., must be provided with sufficient clearance for engine roll and torque.
When a vehicle is equipped with an electronic fuel injection (EFI) engine, it has an engine control module ECM/PCM/TCM or VCM.
This ECM/PCM/TCM or VCM must be maintained at a temperature below 185ºF at all times. This is essential if the vehicle is put
through a paint baking process. The ECM/PCM/TCM or VCM will become inoperative if its temperature exceeds 185ºF. Therefore, it is
recommended that temporary insulation be placed around the ECM/PCM/TCM or VCM during the time the vehicle is in a paint oven
or undergoing another high temperature process.
Note: To protect the under dash, seat locations for control modules must be protected from moisture/water when cleaning vehicle.
Section 7 — Transmission
This product is equipped with a neutral/park start safety switch mounted on the transmission which interfaces with the vehicle starter
circuit. The starter will only operate with the shift lever in the neutral or park position.
Models equipped with brake-transmission shift interlock (BTSI) require full application of the regular brakes before shifting from park
when the ignition key is in the run position.
Section 8 — Fuel and Exhaust
Fuel Systems
Due to the critical nature of sealing the fuel system, anyone making modifications or alterations to the existing system must assume
complete responsibility for the system reliability, performance and compliance to FMVSS 301 and emission standards.
(Section 8 — continued on next page)

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(Section 8 — continued from previous page)
The completed fuel system is certified to be in compliance with the Federal and California Vehicle Emission Standards. Any alterations to
systems or components and their environment could void compliance. Systems include:
• Fuel tank, metering unit, lines including purge control solenoids and canister or canisters.
Environment Includes:
• Heat sources, heat shields, system component relocation.
For these reasons, NO ALTERATION OF THE FUEL SYSTEM IS RECOMMENDED.
If the fuel system is received from the manufacturer in an incomplete condition, certification becomes the responsibility of the
intermediate or final stage manufacturer.
Fuel Fill
Fuel tank filler pipe location should be so situated and constructed as to prevent gasoline vapor from emitting to vents of pilot flamed
devices and to body and engine compartment air inlets.
It is recommended that when mounting the fuel filler pipe assembly and vent hose that a minimum of 3.0 in. clearance be provided to any
body component to prevent contact between hoses and/or mating parts and that retention be provided to ensure routing and prevent
failure due to wear and fatigue. Filler pipe and vent line must have a gravity fuel flow to tank at all times; no fuel traps are allowed.
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.
This vehicle is equipped with concentric fuel fill and vapor lines made from special materials in order to meet the Federal and California
Evaporative Emission Standards. Changing the length, material, and/or routing of the fuel fill will require evaporative emission validation
by the final stage manufacturer.
Fuel Lines
Fuel line routing precautions:
• 12 in. minimum clearance to exhaust system is required or a metal shield must be provided.
• Fuel lines should be clipped (every 600 mm or less) to prevent chafing. Metal clips must have rubber or plastic liners.
(Section 8 — continued on next page)

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(Section 8 — continued from previous page)
• 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. Fuel supply is pressurized by an in-tank pump. Coupled hose or electrically
conductive quick-connect must be used.
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.
Fuel Tank
The tank must have a minimum clearance of 2 in. top, front, rear and side to 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. Pressures greater
than this amount may be detrimental and affect tank durability.
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.
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Gaseous Fuel Conversions
All truck gasoline engines may be converted to use liquified petroleum gas (LPG) or natural gas (NG). Some conversions may cause
harmful effects to the engine. Such fuel systems may require assurances from alternate fuel system manufacturers and/or installers that
the equipment will not cause damage to the engine or the exhaust system.
In the use of dual fuel systems, the intermediate or final stage manufacturer should strictly adhere to the manufacturer’s procedures for
switching from gasoline to gaseous fuel operation. Improper switching procedures may result in overheating and damage to the exhaust
system and the vehicle. The gaseous fuel tank should not be mounted in an enclosed area of the vehicle, such as the passenger
compartment, etc., and the system should be vented to the outside of the vehicle. In addition, vehicles converted to gaseous fuels should
not be stored in enclosed places such as garages. Further, General Motors cautions purchasers that the design, location and installation
of any type of fuel storage system involves significant technical and engineering considerations and that these statements on gaseous
fuel conversions should not be interpreted to be an approval by General Motors of any modification to the original equipment fuel system.
Conversions to gaseous fuel should be made in conformance with applicable Federal and State regulations. Removal of emission-control
components and/or the addition of gaseous fuel systems, which could damage or reduce the longevity of those components, could
cause the mechanical and emission performance warranty to be voided.
Exhaust System
Particular care should be taken to prevent the possibility of exhaust fumes and carbon monoxide exposure to vehicle occupants in units
completed by body builders. Holes and openings through the floor and all other parts of the body must be permanently and adequately
sealed by the body builder to avoid exhaust intrusion into any occupant area. If it is necessary to change the exhaust outlet location, the
exhaust discharge must be unobstructed and directed away from occupant areas. Alteration of the exhaust outlet or its position may
increase exhaust noise and render the vehicle illegal in those areas with pass-by noise regulations. All vehicles >10,000 lbs. GVWR come
under Federal noise regulations, vehicles ≤10,000 lbs. GVWR are regulated by various state and local regulations of the Environmental
Protection Agency; see those regulations for rules, test procedure and noise levels permitted.
Check for proper clearance between body members and chassis components which may in any way affect the reliability and
performance of the vehicle by developing abrasion and wear points from moving parts or degradation from extreme environment or
thermal exposure or may increase interior noise. Any attachments must consider chassis components for jounce and rebound motion at
maximum GVW.
Tail pipe outlet location must be tested statically and with the vehicle in motion to ensure that exhaust gases do not enter through side or
rear windows or underbody seams and holes. Auxiliary power plants should also be tested under the same conditions. Tail pipe exit
ahead of rear wheels is not recommended.
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Check for leaks in exhaust systems and repair as required.
NOTE: The manifold joint take down pipe and converter assembly incorporating oxygen sensors is designed to suit OBD II
requirements, which are dependent upon specific gas leakage rates at the joints. Ideally this assembly should not be
disturbed during the body manufacturing process.
Exhaust gas temperatures can exceed 1600ºF under extreme operating conditions, with pipe surface temperatures slightly less than this.
Extreme care must be used when placing body components in the proximity of the exhaust system so as not to exceed the rated
temperature limits of the components. Due to variants in underbody configurations of the vehicles, General Motors is not in a position to
make recommendations on how to insulate or design components in the proximity of the exhaust system.
Each manufacturer must make temperature checks of critical areas and adjust his design accordingly, or provide shielding to ensure safe
operation of body components.
The same can be said for the engine compartment. Obviously there will be additional heat radiated from the engine. How much is retained
in the area will depend on how well the area is ventilated in your individual designs. Here again, temperature checks of interior areas
surrounding the engine should be made to determine if your insulation is adequate. This is the same engineering practice General Motors
has followed on our complete vehicles incorporating these exhaust systems.
Exhaust system materials are selected and tested to withstand the operating environment of the vehicle. Do not modify the exhaust
system in any way. The tail pipes are made of 409 aluminized stainless steel.
Heat shields are mounted to the chassis, underbody and/or exhaust system components (tail pipe).
Section 9 — Steering
Check power steering fluid level and system operations. (Refer to Owner’s Manual).
Steering wheel and horn pad must not be altered or replaced.
The steering column mast jacket must not be altered.
The steering column must be locked or pinned to prevent rotation when the steering gear or column-to-gear intermediate shaft is
disconnected. Damage to the inflatable restraint control wire can result if this is not done (see Service Manual).

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Section 10 — Tires
Check wheel lug nuts for proper torque; specifications are provided in the Owner’s Manual.
Substitution of tires of greater capacity than those offered as original equipment by vehicle manufacturer is not approved for use on
original equipment wheels. Any usage of higher capacity tires must be accompanied by higher capacity wheels. However, the wheel
offset and distance from centerline of rim to wheel mounting face must be the same as the replaced original equipment wheel to ensure
proper wheel bearing loading and clearance of tires to body and chassis components.
Increasing tire and wheel capacity does not increase vehicle GVW ratings.
It is recommended that tire chain clearance guideline from the Society of Automotive Engineers, J683, be adhered to in designing rear
wheelhouse clearance.
Check tires and inflate to recommended tire pressure according to the tire pressure information provided in the Owner’s Manual and tire
inflation label provided with the vehicle.
Any substitution of tires may affect Speedometer/Odometer accuracy, tire wear, fuel economy, ride and handling and stopping distances.
Section 12 — Electrical Battery and Battery Cables
The vehicle battery should be located and positioned to make use of the existing battery cables. If the battery requires relocation and
longer cables are required, a proportionately larger gauge wire must be used. If, in relocating the battery, the negative ground cable is
attached to the frame rail, a cable of similar gauge must be provided between the frame rail and the engine. This is required due to the
heavy electrical loads imposed by the starting circuit. To ensure proper operation of the battery cables the following chart on length,
gauge and materials must be strictly adhered to.
Combined Length of Positive and Negative
Cable Gauge Cable in Inches (Copper)
466
2107
0170
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Battery Installation
The battery and cable installation, provided by the body upfitter, must comply with the following guidelines. Non-compliance may result
in a failure of the vehicle electrical component system, the shutdown of the engine or the possibility of fire.
1. The cables must not contact any sharp edge(s), in either the normal (stored) or slid (maintenance) position (school bus
application).
2. The cables must not be bent in a radius of smaller than 10 times the cable diameter. Insulation failure can occur if this happens.
3. The cable must be supported by clips spaced at a distance of not more than 250 mm. In this clipping, they shall not have a free
movement that will allow rubbing on any vehicle component, either fixed or moveable.
4. All clips used must be of the rubber-lined type, not rubber dipped.
5. Do not splice the battery cables. Cable modifications can result in vehicle starting problems and loss of other key systems.
6. The cables must be clipped to the battery tray such that the cable pull loads are not transferred into the battery posts due to
slide tray movement. Failure to do so can result in loose terminals, poor starting or battery failure. Battery acid leakage could
result around posts not properly relieved of strain.
7. The cable attachments at the battery terminal must not cause undue strain at these connections. There should be no sharp
bends in the cables adjacent to the connections. The cables should be routed down from the terminals rather than horizontally
from the terminals to prevent a lever action that may loosen connections. Terminal corrosion inhibitors and other coatings
should not be applied to the sealed electrical contact areas. Terminal torque of the sealed terminal shall be 10/20 N•m freedom,
14/20 N•m linehaul.
8. Mounting Base (Tray) – The tray should be of a substantial material sufficiently reinforced to resist flexing and cracking. The tray
must provide firm, continuous support of the battery and not amplify vibration levels. There must be no protrusions or projec-
tions in the tray or mountings that would damage the battery. Cantilevered mountings are not recommended and the tray
should be mounted flat so as not to aggravate electrolyte spillage or lead fatigue. A rounded lip of adequate height to ensure
stiffness and retention should be provided around the perimeter of the tray. With the battery mounted in a vehicle, a static force
of 22 kg applied to a 6.54 sq. cm. area at any corner should not move the battery any more than .25 mm.
Battery trays are supplied with the chassis. In the case of motor homes and diesel school buses, the trays are secured to the
frame rail. The trays shipped on the rails may be relocated to other areas on the vehicle, keeping in mind the recommendations
noted above.
For other units, the tray is supplied on the radiator support.
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