
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.
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 3-31for more information.
What to Use
To determine what kind of fluid to use, seePart C:
Recommended Fluids and Lubricants on page 6-32.
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.
5-45

Single Axle Models
Item Number Item Remarks
1 Brake Camshaft** One fitting each (apply sparingly).
2 Steering Column Slip Joint* One fitting.
3 Steering Drag Link Ends One fitting each end.
5-52

Item Number Item Remarks
4 Pivot Points and Hinges Apply chassis lubricant.
5 Pivot Points and Hinges Apply chassis lubricant.
6 Slack Adjuster** One fitting.
7Brake Cam Roller Pins at interface
of pin and shoe**Apply engine oil.
8 Front Steering KnucklesOne fitting each side, lower bushing.
(Hand-operated grease gun only.)
Hand-pack upper bearing.
9 Front Wheel Bearings Hand-pack or lubricate.
10 Steering Tie Rod Ends One fitting each end.
11 Spring Slip Pads* (Multi-Leaf Only) Apply chassis lubricant.
12 Clutch Release Bearing* Cup or fitting.
13 Battery Terminal (except “ST” type) Keep coated with petroleum jelly.
14 Transmission Fill to level of filler plug.
15 Propshaft U-JointsLubricate with GM Part No. 1051344 Wheel
Bearing Lubricant.
16 Parking Brake Clevis Pin$ Apply chassis lubricant.
17 Parking Brake Lever Pivot*, $ Apply chassis lubricant.
18Clutch Release Cross Shaft,
Master Cylinder$Apply chassis lubricant, fill to 1/4 inch (6 mm)
below opening.
19 Release Bearing, Clutch Cross Shaft Two fittings, apply chassis lubricant.
20 Clutch Release Fork Two fittings.
* Applies to some vehicles.
** Applies to air brakes only.
$ Applies to hydraulic brakes only.
5-53

When you replace tires, make sure they are the same
size, load range, speed rating and construction type
(bias, bias-belted or radial) as your original tires.
If your vehicle has four-wheel drive, the axle differentials,
propshafts and transfer case may be damaged if tires
of different sizes, brands or tread types are installed on
the front and rear axles. That damage would not be
covered under your warranty.
Wheel Alignment and Tire Balance
The wheels on your vehicle were aligned at the
factory to give you the longest tire life and best overall
performance.
Proper front wheel alignment must be maintained in
order to ensure efficient steering, good directional
stability, and prevent abnormal tire wear. If you notice
unusual tire wear or your vehicle is pulling one way
or the other, the alignment may need to be reset. If you
notice your vehicle vibrating when driving on a smooth
road, your wheels may need to be balanced.
Tightening the Wheel Nuts
{CAUTION:
Wheel nuts that are not tight can work loose. If
all the nuts on a wheel come off, the wheel can
come off the vehicle, causing a crash. All
wheel nuts must be properly tightened. Follow
the rules in this section to be sure they are.
This section lets you know how often to check the
tightness of the wheel nuts on your vehicle and how tight
they must be.
5-73

Used Replacement Wheels
{CAUTION:
Putting a used wheel on your vehicle is
dangerous. You cannot know how it has been
used or how far it has been driven. It could fail
suddenly and cause a crash. If you have to
replace a wheel, use a new GM original
equipment wheel.
If a Tire Goes Flat
It’s unusual for a tire to “blow out” while you’re driving,
especially if you maintain your tires properly. If air
goes out of a tire, it’s much more likely to leak out
slowly. But if you should ever have a “blow out,” here
are a few tips about what to expect and what to do:
If a front tire fails, the flat tire will create a drag that pulls
the vehicle toward that side. Take your foot off the
accelerator pedal and grip the steering wheel firmly.
Steer to maintain lane position, and then gently brake to
a stop well out of the traffic lane.A rear blowout, particularly on a curve, acts much like a
skid and may require the same correction you’d use
in a skid. In any rear blowout, remove your foot from the
accelerator pedal. Get the vehicle under control by
steering the way you want the vehicle to go. It may be
very bumpy and noisy, but you can still steer. Gently
brake to a stop –– well off the road if possible.
If a tire goes flat, avoid further tire and wheel damage
by driving slowly to a level place and turn on your
hazard warning flashers.
{CAUTION:
Your vehicle, when new, did not include tire
changing equipment or a place to store a tire
in the vehicle. Special tools and procedures
are required if a tire needs to be serviced. If
these tools and procedures are not used, you
or others could be injured or killed while trying
to change or service a truck tire.
Your truck, when new, did not include tire changing
equipment or a place to store a tire in the vehicle. Few
drivers of these vehicles have the necessary equipment
aboard to be able to change a flat tire safely.
5-78

Part GM Part Number ACDelco®Part Number
Fuel Filter
6.6L 97385488 TP1298A
7.2L — 915 Primary**
7.8L 94392474 —
8.1L — GF626*
Power Steering Fluid Filter 88892858 —
Pressure Caps
6.6L; 7.8L 15075118 —
7.2L — —
8.1L 15997145 —
Secondary Fuel Filter
6.6L — —
7.2L — 1R0751††
7.8L 15098649 —
8.1L 25055052 —
Spark Plugs
6.6L — —
7.2L — —
7.8L — —
8.1L 12578277 41-983
*Optional Davco (K28) D350921 spin-on type filter located on driver’s side frame rail.
**Optional Cold Weather (KUK) Racor B6484GM spin-on type filter located on driver’s side frame rail.
***Optional air filter (GM Part No. 88937525) for C6/C7/C8 Models. Fits inside standard size filter
(GM Part No. 88937548) listed previously.
†Donaldson part number.
††CAT part number.
See the Allison Transmission
®Operator’s Manual in your vehicle for external filter part numbers and information.
5-101

❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (5)
❑Gasoline Engine: Inspect engine air cleaner filter. If
necessary, replace the filter. If vehicle is driven in
dusty/dirty conditions, inspect filter at every engine oil
change. SeeEngine Air Cleaner/Filter on page 5-33
for more information.
❑Diesel Engine: Inspect engine air cleaner filter change
indicator. If necessary, replace the filter. If vehicle is
driven in dusty/dirty conditions, inspect filter change
indicator at every engine oil change. SeeEngine Air
Cleaner/Filter on page 5-33for more information.
❑DURAMAX
®Diesel Only: Replace fuel filter (or every
750 hours of engine operation, whichever occurs first).
❑Steering system service.(12)
❑Front and rear suspension service.(13)
❑Spring-to-axle U-bolts and shackle bolts service.(15)
❑Exhaust system service (or every 6 months, whichever
occurs first).(2) (3) (16)
❑Wheels and tires service.(14)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(6) (36)❑Parking brake service (or every 6 months, whichever
occurs first).(21)
❑Air brake service (or every 6 months, whichever
occurs first).(32)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(33)
❑Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours, whichever
occurs first).
❑Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first). Lubricate
linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(34)
❑Thermostatically controlled engine cooling fan
service.(3) (19)
❑Shields and underhood insulation service.(3) (4) (20)
❑Air compressor dry element pleated paper air strainer
service (or every 2 months or every 800 hours,
whichever occurs first).
6-7

24,000 Miles (40 000 km)
❑7.8L DURAMAX®Diesel Without Engine Oil Life
System Only: Change engine oil and filter (or
every 12 months, or every 600 hours of engine
operation, whichever occurs first).(2)
❑7.8L DURAMAX
®Diesel With Engine Oil Life System
Only: Check oil life system (or every 600 hours of
engine operation, whichever occurs first). If engine oil
and filter are changed, reset system. See “Engine
Oil (DURAMAX
®Diesel)” in the Index.(2) (7)
30,000 Miles (48 000 km)
❑Gasoline Engine Only: Check engine oil life system. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(2) (8)
❑6.6L DURAMAX
®Diesel Without Engine Oil Life
System Only: Change engine oil and filter (or every
12 months, or every 750 hours of engine operation,
whichever occurs first).(2)
❑6.6L DURAMAX
®Diesel With Engine Oil Life System
Only: Check oil life system. If engine oil and filter are
changed, reset system. See “Engine Oil (DURAMAX
®
Diesel)” in the Index.(2) (9)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (5)❑Gasoline Engine: Inspect engine air cleaner filter. If
necessary, replace the filter. If vehicle is driven in
dusty/dirty conditions, inspect filter at every engine oil
change. SeeEngine Air Cleaner/Filter on page 5-33
for more information.
❑Diesel Engine: Inspect engine air cleaner filter change
indicator. If necessary, replace the filter. If vehicle is
driven in dusty/dirty conditions, inspect filter change
indicator at every engine oil change. SeeEngine Air
Cleaner/Filter on page 5-33for more information.
❑DURAMAX
®Diesel Only: Replace fuel filter (or every
750 hours of engine operation, whichever occurs first).
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(11)
❑Replace fuel filter(s) (or every 12 months, whichever
occurs first).(2)
❑Steering system service.(12)
❑Front and rear suspension service.(13)
❑Spring-to-axle U-bolts and shackle bolts service.(15)
❑Exhaust system service (or every 6 months, whichever
occurs first).(2) (3) (16)
❑Wheels and tires service.(14)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(6) (36)
❑Parking brake service (or every 6 months, whichever
occurs first).(21)
6-9