ISUZU Forward Service Manual
Chevrolet/GMC Class T6500/7500/8500
i
Low Cab Forward
MODEL SYMBOL CHART ...................................................................................................................................................................................1
CHASSIS
& Isuzu Class FTR/FTV/FTX
PAGE
General Arrangement – T6/T7/T8 F042 ....................................................................................................................................................
General Arrangement – T8F064 .................................................................................................................................................................
Body Payload Weight Distribution – T6/T7/T8 F042 ...............................................................................................................................
Body Payload Weight Distribution – T8F064 ............................................................................................................................................
Formulas for Calculating Height Dimensions to Top of Frame – Front Axle .......................................................................................
Formulas for Calculating Height Dimensions to Top of Frame – Rear Axle ........................................................................................
BODY
Cab Exterior – Front, Rear, Side Views – (Cab Tilt, Bumper, Rear Window, Step Heights,
Bumper To BOC, Bumper To Air Induction – Effective CA)....................................................................................................................8
Cab Exterior – Mirrors ................................................................................................................................................................................
Cab Exterior – Door Swings .....................................................................................................................................................................
Cab Interior – Seating ...............................................................................................................................................................................
FRAME
General Information ..................................................................................................................................................................................
Section Modulus ...............................................................................................................................................................................
Yield Strength ....................................................................................................................................................................................
2
3
4
5
6
7
9
10
11
12
12
12
Resisting Bending Moment (RBM) .................................................................................................................................................
Frame Rail – Material and Weldability ............................................................................................................................................
Body Mounting Concerns ................................................................................................................................................................
Single Axle Medium Duty Conventional .........................................................................................................................................
Strength
Frame Material Properties ...............................................................................................................................................................
Frame Lengths with Reinforcements .....................................................................................................................................................
Frame Lengths with Reinforcements – Charts (042) ............................................................................................................................
Low Cab Forward — Revised 10/2006
..............................................................................................................................................................................................15
12
13
14
14
16
17
18
Low Cab Forward
FRAME – (Continued)
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
ii
PAGE
Frame Lengths with Reinforcements – Charts (064) ............................................................................................................................
Frame and Crossmember Locations (042) .............................................................................................................................................
Frame and Crossmember Locations (064) .............................................................................................................................................
AXLE/SUSPENSION
Front Axle Track and Suspension Drawing ............................................................................................................................................
Front Axle Track Charts ............................................................................................................................................................................
Front Suspension Charts ..........................................................................................................................................................................
Rear Axle and Suspension – Drawing (042) ...........................................................................................................................................
Rear Axle and Suspension – Formulas (042) .........................................................................................................................................
Rear Axle / Suspension – Chart (042) Option Description and Bottom of Differential Bowl ...........................................................
Rear Axle / Wheel – Chart (042) Track Widths .......................................................................................................................................
Rear Axle / Suspension – Chart (042) Heights .......................................................................................................................................
Rear Axle / Suspension – Chart (042) Heights .......................................................................................................................................
Rear Axle and Suspension – Drawing (064) ...........................................................................................................................................
Rear Axle and Suspension – Formulas (064) .........................................................................................................................................
Rear Axle / Suspension – Chart (064) Option Descriptions, Bottom of Differential Bowl and Heights .........................................
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
BRAKES
Air Tank Location – (042) Truck – RQ2 ....................................................................................................................................................
Air Tank Location – (042) Tractor – RQ3 .................................................................................................................................................
Air Tank Location – (064) Truck – RQ2 ....................................................................................................................................................
Air Tank Location – (064) Tractor – RQ3 .................................................................................................................................................
BATTERY BOX LOCATION ................................................................................................................................................................................38
FUEL TANKS
Dual 50 Gallon (opt. NJ8) & Single 50 Gallon LH (opt. NK8)
Dual 50 Gallon LH and 25 Gallon RH (opt. NJ7) & Single 50 Gallon LH (opt. NK6) ...........................................................................
Low Cab Forward — Revised 11/2007
................................................................................................................39
34
35
36
37
40
Chevrolet/GMC Class T6500/7500/8500
Low Cab Forward
AIR INDUCTION .................................................................................................................................................................................................41
EXHAUST
& Isuzu Class FTR/FTV/FTX
iii
PAGE
Single Horizontal Exhaust w/RH exit tailpipe & cooler, opt. N1B & 7.8 Isuzu Diesel LHP & 140´´ WB opt. FQT
Single Horizontal Exhaust w/RH exit tailpipe & cooler, opt. N1B & 7.8 Isuzu Diesel HHP & 140´´ WB opt. FQT
Single Horizontal Exhaust, opt. NB5 & 7.8 Isuzu Diesel LHP & 152´´ and longer WB
Single Horizontal Exhaust, opt. NB5 & 7.8 Isuzu Diesel HHP & 152´´ and longer WB
Exhaust LH Vertical DPF, Tailpipe and Heat Shield – Exhaust opt. NEP, with Engine opt. LF8, 7.8L LHP Isuzu ...........................
Exhaust LH Vertical DPF, Tailpipe and Heat Shield – Exhaust opt. NEP, with Engine opt. LF8, 7.8L HHP Isuzu ..........................
Horizontal Tailpipe, Nozzle, Hangers and Cooler – opt. LF8, 7.8L Isuzu ............................................................................................
PTO
Manual Transmission PTO Location Charts
Automatic Transmission PTO Location Charts
WHEEL & TIRE SPECIFICATIONS ................................. QUICK LINKS – www.gmfleet.com/See Medium Duty Online Order Guide/
Technical Data/Gray Tabs
MODEL & OPTIONS WEIGHTS .......................................QUICK LINKS – www.gmfleet.com/See Medium Duty Online Order Guide/
select model/CALCULATORS
..........................................................................................................................................49
.....................................................................................................................................50
.......................................................................44
......................................................................45
...........................42
..........................43
46
47
48
Low Cab Forward — Revised 11/2007
Chevrolet/GMC Class T6500/7500/8500
Low Cab Forward
& Isuzu Class FTR/FTV/FTX
MODEL SYMBOL CHART
T Series – 2-wheel drive T Series – Tandem
T6F042 T8F064
T7F042
T8F042
MODEL DESIGNATOR KEY:
Position 1 2 3 4 5 6, 7
1
PAGE
Division:
C = Chevrolet
T = GMC
J = Isuzu
General Information:
RPO Code VDS Books
X88 = Chevrolet 11 = Family 3
Z88 = GMC 11 = T Series
Z89 = Isuzu
Low Cab Forward — Revised 10/2006
Division Model GVW Cab Constant Chassis
Line Range Style Type
______ ______ ______ ______ ______ ______
not 0
shown
GVW Range:
Model Line:
T = T Series
6 = 19501 - 26000
7 = 26001 - 33000
8 = Over 33000
Cab Style:
F = Tilt
Chassis Type:
42 = 2 wheel drive
64 = Tandem
Low Cab Forward
General Arrangement – T6/T7/T8 F042
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
2
PAGE
Low Cab Forward — Revised 10/2006
TD006041a
Low Cab Forward
General Arrangement – T8F064
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
3
PAGE
Low Cab Forward — Revised 10/2006
TD006041b
Low Cab Forward
Body Payload Weight Distribution – T6/T7/T8 F042
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
4
PAGE
Low Cab Forward — Revised 10/2006
TD006055a
Low Cab Forward
Body Payload Weight Distribution – T8F064
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
5
PAGE
Low Cab Forward — Revised 10/2006
TD006055b
Sample Data:
Model Tire Tire Loaded Radius LH C D
T7F042
275/80R22.5G (XSH)
18.6" 9.69" 7.35" 5.75"
Frame Reinforcement RPO Wheelbase Suspension RPO Axle RPO
F20 152" (EG9) F28 (12,000 lb) FS7 (12,000 lb)
Formulas:
CH = C + Tire Static Loaded Radius + LH CH = 7.35" + 18.6" + 9.69" = 35.64"
DH = D + Tire Static Loaded Radius + LH DH = 5.75" + 18.6" + 9.69" = 34.04"
Definitions:
C – Centerline of axle to bottom inside of rail at curb position
D – Centerline of axle to bottom inside of rail at design load
LH – Distance from the bottom inside rail to the top of the rail
NOTE: For Tire, Static Loaded Radius (SLR) / QUICK LINKS – www.gmfleet.com /
See Medium Duty Online Order Guide / select Technical Data/Gray Tab from the upper tool bar /
select Wheel-Tire Specification / select print to view.
For the C & D values see the Front Axle and Suspension Chart.
For the LH values see the Frame Length with Reinforcements section.
Step Height Dimensions:
When calculating step height dimensions see the step assembly location, and the frame drawings for values.
R4L/S3L (Michelin) S4L
Low Cab Forward
Formulas for Calculating Height Dimensions to Top of Frame – Front Axle
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
6
PAGE
Low Cab Forward — Revised 10/2006
Sample Data:
Model Tire Tire Loaded Radius LH C D
T7F042
275/80R22.5G (YSH)
19.0" 9.69" 11.41" 7.94"
S3H (Michelin) S4L
Frame Reinforcement RPO Wheelbase Suspension RPO Axle RPO
F20 152" (EG9) GNB (21,000 lb) HPN (21,000 lb)
F
ormulas:
CH = C + Tire Static Loaded Radius + LH CH = 19.0" + 11.41" + 9.69" = 40.11"
DH = D + Tire Static Loaded Radius + LH DH = 19.0" + 7.94" + 9.69" = 36.63"
D
efinitions:
C – Centerline of axle to bottom inside of rail at curb position
D – Centerline of axle to bottom inside of rail at design load
LH – Distance from the bottom inside rail to the top of the rail
NOTE: For Tire, Static Loaded Radius (SLR) / QUICK LINKS – www.gmfleet.com /
See Medium Duty Online Order Guide / select Technical Data/Gray Tab from the upper tool bar /
select Wheel-Tire Specification / select print to view.
For the C & D values see the Rear Axle and Suspension Chart.
For the LH values see the Frame Length with Reinforcements section.
Step Height Dimensions:
When calculating step height dimensions see the step assembly location, and the frame drawings for values.
Low Cab Forward
Formulas for Calculating Height Dimensions to Top of Frame – Rear Axle
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
7
PAGE
Low Cab Forward — Revised 10/2006
Low Cab Forward
Cab Exterior – Front, Rear, Side Views – (Cab Tilt, Bumper, Rear Window,
Step Heights, Bumper To BOC, Bumper To Air Induction – Effective CA)
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
8
PAGE
Low Cab Forward — Revised 10/2006
TD006045a
Low Cab Forward
Cab Exterior – Mirrors
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
9
PAGE
Low Cab Forward — Revised 10/2006
TD006045b
Low Cab Forward
Cab Exterior – Door Swings
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
PAGE
10
Low Cab Forward — Revised 10/2006
TD006045c
Low Cab Forward
Cab Interior – Seating
Chevrolet/GMC Class T6500/7500/8500
& Isuzu Class FTR/FTV/FTX
PAGE
11
Low Cab Forward — Revised 10/2006
TD006044.3
Chevrolet/GMC Class T6500/7500/8500
Low Cab Forward
& Isuzu Class FTR/FTV/FTX
General Information
Section Modulus
• Section modulus is a measure of the frame strength based solely on the height, width, thickness, and configuration of the side
rails. It is calculated at the point of maximum stress, which is usually directly behind the cab.
• Section modulus is not a measure of material strength and can only be used by itself to compare frames of like materials.
• Frame reinforcements will increase the section modulus because they increase the strength by adding to the thickness of the
section.
• Consult the Frame Properties for all section modulus ratings.
Yield Strength
• Yield strength is a measurement of the frame material’s strength. It is maximum load (PSI) that can be placed on the material and
still have it return to its original position when the load is removed without being bent out of shape.
• It can be used only to compare frames of identical section. Two yield strength frames are available for the T-Series. They are
80,000 psi (551,600 kPa) and 120,000 psi (827,400 kPa).
PAGE
12
RBM-Resisting Bending Moment
• Since Section Modulus can only be used to compare frames of like materials and yield strength can only indicate relative strengths
of identical frames, some measurement is necessary to compare frames of different materials and different sections. The RBM,
or Resisting Bending Moment, can be used for this comparison as it utilizes section modulus and yield strength in its makeup.
• RBM = Section Modulus x Yield Strength
• This measurement will show that a smaller section frame of higher strength steel will be just as strong as a larger section frame
of lower strength of steel.
• It is readily apparent that both section modulus and yield strength are equally important so that their product, RBM, is the correct
figure to use for frame comparisons. The RBMs for all standard and optional frames are shown on the Frame Properties charts.
• Frames are designed to torsional stiffness and beaming criteria as well as fatigue strength.
Low Cab Forward — Revised 10/2006
Chevrolet/GMC Class T6500/7500/8500
Low Cab Forward
& Isuzu Class FTR/FTV/FTX
General Information (continued)
Frame Rail – Material and Weldability
• The frames on GM Trucks are built for strength, durability, and adaptability. They are available in tensile strengths of 80,000 psi
(551,600 kPa) and 120,000 psi (827,400 kPa) ratings.
• The 80,000 psi (551,600 kPa) frames are made from hot rolled steel that is pierced and formed to produce a finished side rail.
Following the procedure outlined in the GM Truck Service Manual these frames can be subjected to welding without affecting
frame integrity.
• The 120,000 psi (827,400 kPa) frame rails are made from steel with an initial yield strength of 35,000-40,000 psi. The chemistry
of the steel is slightly different to allow for better handling characteristic.Because the heat treating operation causes molecular
movement in the steel, the only holes pierced in the side rails prior to heat treating are near the front-end hole. Growth can be
predicted in this area and adjustments in hole placement can be made accordingly. The balance of the required holes are pierced
in the frame rail after heat treating.
• The 120,000 psi (827,400 kPa) frame rails are heat treated by an electric induction heat treating process. During this process,
the formed side rails are moved through a series of three induction coils and brought to a temperature of about 1650º F, (898.9º
C). Once at this temperature, the side rail passes through a cold-water quench. After the frame goes through the cold-water
quench, it is very hard but also brittle. Thus, the rails continue to roll through the final “tempering” electric coil and are brought to a
temperature of about 900º F, (482.2º C). Then the frame is allowed to cool to room temperature. This tempering operation “draws”
some of the hardness out of the material, but it now becomes very tough and durable. Once through the tempering operation, the
side rail passes through a “shot peen” operation. This process hurls millions of 1/8-inch, (0.3175 cm), diameter spherical-shaped
balls at the side rails. Shot peening significantly increases the fatigue life of the frame rail, as well as providing a clean surface.
PAGE
13
• Welding should not be preformed on the heat treated 120,000 psi (827,400 kPa) frame rails. Welding depends on heat for a good
adherence. Applying heat or welding on hardened side rails will create a “soft zone” where the heat was applied. Since the heated
area is now softer than the balance of the side rail, the general area would become more susceptible to failure of the frame rail.
Low Cab Forward — Revised 10/2006
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