Service............................................................5-4
Accessories and Modifications..........................5-4
California Proposition 65 Warning.....................5-5
California Perchlorate Materials Requirements.....5-5
Doing Your Own Service Work.........................5-6
Engine Fan Breakage.....................................5-6
Fuel................................................................5-7
Gasoline Octane............................................5-7
Gasoline Specifications....................................5-7
Additives.......................................................5-8
Diesel Engine Fuel.........................................5-9
What Fuel to Use...........................................5-9
Very Cold Weather Operation.........................5-12
Water in Fuel...............................................5-12
Running Out of Fuel.....................................5-17
Fuel Filter Replacement.................................5-18
Fuels in Foreign Countries.............................5-19
Filling the Tank............................................5-20
Filling a Portable Fuel Container.....................5-21
Checking Things Under the Hood....................5-22
Hood Latches...............................................5-22
Engine Oil (Caterpillar
®Diesel Engine).............5-23
Engine Oil (Gasoline Engine)..........................5-24
Engine Oil (DURAMAX
®Diesel Engine)............5-28Engine Oil (Isuzu Diesel Engine).....................5-32
Engine Oil Life System (Gasoline Engine)........5-36
Engine Oil Life System (DURAMAX
®/Isuzu
Diesel Engines).........................................5-37
Engine Oil Life System (Caterpillar
®Diesel
Engine)....................................................5-39
Engine Air Cleaner/Filter................................5-39
Automatic Transmission Fluid.........................5-43
Manual Transmission Fluid.............................5-43
Engine Coolant (Caterpillar
®Diesel Engines).....5-44
Engine Coolant (Gas and DURAMAX®/
Isuzu 7.8L L6 Engines)..............................5-44
Coolant Surge Tank Pressure Cap..................5-47
Engine Overheating.......................................5-48
Cooling System............................................5-50
Engine Fan Noise.........................................5-54
Power Steering Fluid.....................................5-54
Windshield Washer Fluid................................5-55
Brakes........................................................5-57
Battery........................................................5-66
Jump Starting...............................................5-67
Rear Axle.......................................................5-72
Rear Axle Shift Motor....................................5-73
Section 5 Service and Appearance Care
5-1
4. With the coolant surge tank pressure cap off, start
the engine and let it run until you can feel the upper
radiator hose getting hot. Watch out for the engine
cooling fan.
By this time, the coolant level inside the coolant
surge tank may be lower. If the level is lower, add
more of the proper mixture to the coolant surge tank
until the level reaches slightly above the FULL
COLD mark.
5. Then replace the pressure cap. Be sure the
pressure cap is hand-tight and fully seated.
Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions, the clutch is not fully engaged. This improves
fuel economy and reduces fan noise. Under heavy
vehicle loading, trailer towing and/or high outside
temperatures, the fan speed increases when the clutch
engages. So you may hear an increase in fan noise. This
is normal and should not be mistaken as the transmission
slipping or making extra shifts. It is merely the cooling
system functioning properly. The fan will slow down when
additional cooling is not required and the clutch
disengages.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch disengages.
Power Steering Fluid
SeeScheduled Maintenance on page 6-5to determine
when to check your power steering fluid.
5-54
How To Check Power Steering Fluid
Check your power steering fluid only when the engine is
warm. If the engine is not warm, you probably will not
get an accurate reading.
If the fluid level is between the MIN (Minimum) and
MAX (Maximum) marks, you have enough. If you need
fluid, add only enough of the proper fluid to bring it in
between the MIN and MAX marks.
If your power steering fluid level is low, this can cause
the brake or service brakes soon warning lights to come
on. In addition, the steering effort and emergency brake
distance could increase.
If either light remains on after you have added power
steering fluid to the proper level, then shut off the engine
for 10 seconds. This should reset the brake warning
lights. If one or both lights stay on, see “Hydraulic Brake
System Warning Lights” underBrake System Warning
Light on page 3-32for more information.
What to Use
To determine what kind of fluid to use, see
Part C: Recommended Fluids and Lubricants on
page 6-31.
Notice:When adding power steering uid or
making a complete uid change, always use the
proper uid. Failure to use the proper uid can
cause leaks and damage hoses and seals.
Windshield Washer Fluid
What to Use
When you need windshield washer fluid, be sure to read
the manufacturer’s instructions before use. If you will be
operating your vehicle in an area where the temperature
may fall below freezing, use a fluid that has sufficient
protection against freezing.
5-55
Part GM Part Number ACDelco®Part Number
Fuel Filter
6.6L V8 97385488 TP1298A
7.2L L6 — 1R-0751††
Isuzu 6H 98026037 —
8.1L V8 (C4/C5 with NG6/NK1 or U-Haul) 21998364 —
8.1L V8 (C4/C5 with all other fuel tanks) 10376257 —
8.1L V8 (All C6/C7/C8) 10370247 —
Power Steering Fluid Filter 88892858 —
Secondary Fuel Filter
6.6L V8 — —
7.2L L6 (NWB) 15618921 —
Isuzu 6H 25014274 TP915D
Isuzu 6H (KUK) 88983117 TP1519
8.1L V8 (K28 and standard U-Haul) 25014476 TP1247
Spark Plugs
6.6L V8 — —
7.2L L6 — —
Isuzu 6H — —
8.1L V8 12578277 41-983
1Optional air filter (GM Part No. 88937548 AC Delco No. A2035C) for C6/C7/C8 Models. Fits inside standard size
filter (GM Part No. 88937525 AC Delco No. A2031C) listed previously.
†Racor part number.
††Caterpillar
®part number.
See the Allison Transmission®Operator’s Manual in your vehicle for external filter part numbers and information.
5-116
Part C: Recommended Fluids and
Lubricants
Fluids and lubricants identified below by name, part
number, or specification can be obtained from your
dealer/retailer.
Usage Fluid/Lubricant
Engine Oil
(Gasoline
Engine)Engine oil which meets
GM Standard GM6094M and
displays the American Petroleum
Institute (API) Certified for Gasoline
Engines starburst symbol. To
determine the proper viscosity for
your vehicle’s engine, see “Engine
Oil” in the Index.
Engine Oil
(DURAMAX
®/
Isuzu Diesel
Engines)Engine oils with the letters CJ-4 are
required for your vehicle. The CJ-4
designation can appear either alone
or in combination with other
American Petroleum Institute (API)
designations, such as API CJ-4/SL.
These letters show API levels of
quality. To determine the preferred
viscosity for your vehicle’s diesel
engine, see “Engine Oil” in the Index.
Engine Oil
(Caterpillar
®
Diesel Engine)See the Caterpillar
®Operation &
Maintenance Manual for engine oil
recommendations.
Usage Fluid/Lubricant
Engine Coolant
(Caterpillar
®
Diesel Engine)See the Caterpillar
®Operation &
Maintenance Manual for engine
coolant recommendations.
Engine Coolant
(Gasoline
Engine &
DURAMAX
®/
Isuzu Diesel
Engines)50/50 mixture of clean, drinkable
water and use only DEX-COOL
®
Coolant. SeeEngine Coolant
(Caterpillar®Diesel Engines) on
page 5-44orEngine Coolant
(Gas and DURAMAX
®/Isuzu 7.8L
L6 Engines) on page 5-44.
Hydraulic Brake
SystemDelco
®Supreme 11 Brake Fluid or
equivalent DOT-3 brake fluid.
Windshield
Washer SolventOptikleen
®Washer Solvent.
Clutch Bearing
LubricantClutch Bearing Lubricant
(GM Part No. 12378484 or
equivalent NLGI #3 consistency).
Exhaust Brake
Ball Joint Cap
LubricantHigh-Temperature Grease
(GM Part No. U.S. 1051344, in
Canada 903037) or NLGI #3
consistency.
Power Steering
SystemDEXRON
®-VI Automatic
Transmission Fluid.
Manual
TransmissionSynthetic Manual Transmission Fluid
(GM Part No. U.S. 88861952, in
Canada 88861953).
6-31
Exhaust Brake Indicator Light...........................3-40
Exhaust Restrictor...........................................2-22
Extender, Safety Belt.......................................1-28
Exterior Lamps...............................................3-14
F
Filter
Engine Air Cleaner......................................5-39
Filter Minder Gage..........................................3-45
Finish Damage...............................................5-99
Fixed Mast Antenna........................................3-58
Flashers, Hazard Warning.................................. 3-6
Flat Tire........................................................5-92
Fluid.............................................................5-43
Power Steering...........................................5-54
Windshield Washer......................................5-55
Four-Wheel Drive....................................2-32, 5-73
Front Axle......................................................5-74
Front Wheel Bearings with Oil-Filled Hubs..........5-81
Fuel............................................................... 5-7
Additives...................................................... 5-8
Change Filter Warning Light..........................3-44
Diesel Engine Fuel........................................ 5-9
Filling a Portable Fuel Container....................5-21
Filling the Tank...........................................5-20
Filter..........................................................5-78
Filter Replacement.......................................5-18
Fuels in Foreign Countries............................5-19Fuel (cont.)
Gage.........................................................3-43
Gasoline Octane........................................... 5-7
Gasoline Specifications.................................. 5-7
Primary Filter and Water Separator................5-79
Running Out of...........................................2-50
Running Out of Fuel....................................5-17
Secondary Filter and Water Separator/
Heater....................................................5-80
Very Cold Weather Operation........................5-12
Water in Fuel..............................................5-12
Water in Warning Light.................................3-44
What Fuel to Use.......................................... 5-9
Fuses
Fuses and Circuit Breakers.........................5-103
Instrument Panel Fuse Block.......................5-103
Underhood Fuse Block...............................5-106
Windshield Wiper.......................................5-102
G
Gage
Air Pressure...............................................3-46
Check Gages Warning Light..........................3-42
Engine Coolant Temperature.........................3-35
Filter Minder...............................................3-45
Fuel..........................................................3-43
Hourmeter..................................................3-46
Oil Pressure...............................................3-37
5
Outlet Adjustment............................................3-23
Outlets
Accessory Power.........................................3-19
Outside
Convex Mirrors............................................2-52
Heated Mirrors............................................2-52
Manual Mirrors............................................2-51
Power Mirrors.............................................2-51
Overspeed Warning Light.................................3-39
P
Paint, Damage...............................................5-99
Park Brake............................................2-38, 2-41
Parking.........................................................2-37
Brake Burnish Procedure..............................2-43
Over Things That Burn.................................2-44
Two-Speed Rear Axle..................................2-27
Part A - Scheduled Maintenance Services............ 6-3
Part B - Owner Checks and Services................6-25
Part C - Recommended Fluids and Lubricants....6-30
Part D - Maintenance Record...........................6-32
Passing.........................................................4-11
Perchlorate Materials Requirements, California...... 5-5
Power
Door Locks.................................................. 2-7
Electrical System.......................................5-103
Reduced Engine Light..................................3-41Power (cont.)
Steering Fluid.............................................5-54
Windows...................................................... 2-9
Power Take-Off Light.......................................3-42
Power Take-Off (PTO).....................................2-32
Privacy..........................................................7-11
Event Data Recorders..................................7-11
Navigation System.......................................7-12
OnStar.......................................................7-12
Radio Frequency Identification.......................7-12R
Radio Frequency Identification (RFID), Privacy....7-12
Radios..........................................................3-47
Radio(s)........................................................3-48
Radios
Reception...................................................3-58
Setting the Clock.........................................3-48
Theft-Deterrent............................................3-57
Range Inhibit Warning Indicator........................3-32
Reading Lamps..............................................3-17
Rear Axle......................................................5-72
Differential Lock Control................................. 4-7
Shift Motor.................................................5-73
Rear Heating System......................................3-24
Rear Seat Operation.......................................1-10
Rearview Mirrors.............................................2-51
9