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Rear Axle Shift Motor
When to Check and Change Fluid
If you have an optional air-shift two-speed,
controlled traction, or locking differential type rear
axle, a good time to check the fluid level in the axle
shift motor is when the rear axle lubricant is
checked.
How to Check Fluid
Remove the plug on the front plate of the axle
shift motor, add enough fluid to raise the level to
the bottom of the filler plug hole, then replace
the plug.
What to Use
Refer to your Maintenance Schedule to determine
what kind of lubricant to use. SeePart C:
Recommended Fluids and Lubricants on page 397.
Four-Wheel Drive
Transfer Case
When to Check Lubricant
It is not necessary to regularly check transfer case
fluid unless you suspect there is a leak or you
hear an unusual noise. A fluid loss could indicate
a problem. Have it inspected and repaired.
How to Check Lubricant
A. Fill Plug
B. Drain Plug
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Page 319 of 430

To change an empty ether cylinder, follow
these steps.
1. Loosen the screw head on the
cylinder-to-bracket clamp.
2. Spread the clamp apart.
3. Clean any dirt from the neck of the cylinder
and the top of the valve before you take out
the cylinder.
4. Check the inside of the valve for any foreign
matter. Clean the valve as necessary.
5. Cover the valve to protect it from dirt and take
out the cylinder.
6. Install a new gasket whenever you take out
the cylinder. Use only one gasket and spread
a light film of clean oil on it before installation.
7. Put in the new cylinder. Turn it clockwise until
it just starts to contact the gasket.
8. Tighten the cylinder another half turn
(180 degrees). Don’t over-tighten.
9. Retighten the cylinder clamp.Front Wheel Bearings with
Oil-Filled Hubs
Notice:If you drive your vehicle through deep
water that is higher than the front or rear
axle, water may enter the axle housing and
cause the axle lubricant to break down.
This could damage the gears inside. Avoid
driving your vehicle through deep water.
You should avoid driving your vehicle through
deep puddles or standing water. If you must drive
through water that is higher than the front or
rear axle, see your dealer immediately afterward
to have the condition of the axle lubricant checked.
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Page 323 of 430

Wheel Loading
Wheels are stamped with a maximum load and
cold inflation rating. Be sure you do not exceed
these limits. If you ever think you need to exceed
these limits, first contact the rim and wheel
maker to get their advice.
Dual Tire Operation
When the vehicle is new, check the wheel nut
tightness on all wheels with a torque wrench after
your first 100 miles (160 km) and then 1,000 miles
(1 600 km) after that. Whenever a wheel, wheel
bolt or wheel nut is removed or serviced,
repeat the 100 miles (160 km), and then 1,000 mile
(1 600 km) wheel nut tightness check.SeeTightening the Wheel Nuts on page 325for
wheel nut tightening information and proper
torque values.
{CAUTION:
If you operate your vehicle with a tire that
is badly underin ated, the tire can
overheat. An overheated tire can lose air
suddenly or catch re. You or others could
be injured. Be sure all tires (including the
spare, if any) are properly in ated.
SeeTires on page 321andIn ation - Tire
Pressure on page 322for more information on
proper tire inflation.
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Page 324 of 430

When It Is Time for New Tires
Replace your tires when the tread depth is down
to 1/8 of an inch (3.2 mm) for the front tires,
or 1/16 of an inch (1.6 mm) for a rear tire. Also,
you need a new tire if:
•You can see cord or fabric showing through
the tire’s rubber.
•The tread or sidewall is cracked, cut or
snagged deep enough to show cord or fabric.
•The tire has a bump, bulge or split.
•The tire has a puncture, cut or other damage
that cannot be repaired well because of the
size or location of the damage.
{CAUTION:
Mixing tires could cause you to lose
control while driving. If you mix tires of
different types — like radial and
bias-belted tires — the vehicle may not
handle properly, and you could have a
crash. Be sure to use the same type of
tires all around.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.
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Page 325 of 430
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.
First, use these pictures to decide what kind of
wheels you have.Then, refer to the following steps for the wheels
you have.
Hub-Piloted Wheels, 8-Hole or 10-Hole
The studs and nuts used with these wheels have
right-hand threads.
1. With intermittent pilot pads, position a pad at
12 o’clock to center the wheel and reduce
run-out.
2. Put the tire and rim assembly on the axle hub.
Install the outer rear tire and rim assembly so
that its valve stem is exactly opposite the
valve stem on the inner tire and rim assembly.
Hub-Piloted Type,
8-HoleHub-Piloted Type,
10-Hole
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Page 326 of 430
3. Put on the wheel nuts.
4. Finger-tighten the nuts.
5. Oil the surfaces (B)
between the nuts (C)
and washers (A).
Do not oil the
studs or the threads
of the nut.
6. Tighten the nuts to 400 lb ft (542
Y)ifan
8-hole stud or 480 lb ft (650
Y) if a 10-hole
stud, using the following diagrams.
8-Hole
10-Hole (Front)10-Hole (Rear)
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{CAUTION:
Never use oil or grease on studs or the
threads of the wheel nuts. If you do, the
wheel nuts might come loose and the
wheel could fall off, causing a crash.
{CAUTION:
If wheel studs are damaged, they can
break. If all the studs on a wheel broke, the
wheel could come off and cause a crash. If
any stud is damaged because of a
loose-running wheel, it could be that all of
the studs are damaged. To be sure, replace
all studs on the wheel. If the stud holes in a
wheel have become larger, the wheel could
collapse in operation. Replace any wheel if
its stud holes have become larger or
distorted in any way. Inspect hubs and
CAUTION: (Continued)
CAUTION: (Continued)
hub-piloted wheels for damage. Because
of loose running wheels, piloting pad
damage may occur and require
replacement of the entire hub, for proper
centering of the wheels. When replacing
studs, hubs, wheel nuts or wheels, be
sure to use GM original equipment parts.
{CAUTION:
Rust or dirt on a wheel, or on the parts to
which it is fastened, can make wheel nuts
become loose after a time. The wheel could
come off and cause a crash. When you
change a wheel, remove any rust or dirt
from places where the wheel attaches to
the vehicle. In an emergency, you can use a
cloth or a paper towel to do this; but be
sure to use a scraper or wire brush later, if
you need to, to get all the rust or dirt off.
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How Often to Check
Wheel tightness is so important you should have a
technician check nut tightness on all wheels with a
torque wrench after your first 100 miles (160 km),
and then 1,000 miles (1 600 km) after that. Be sure
to repeat this service whenever you have a tire
removed or serviced. SeeScheduled Maintenance
on page 363for further information.
Wheel Replacement
Replace any wheel that is bent, cracked or badly
rusted or corroded. If wheel nuts keep coming
loose, replace the wheel. If the wheel leaks
air, replace it.
Your dealer will know the kind of wheel you need.
Each new wheel should have the same
load-carrying capacity, diameter, width, offset and
be mounted the same way as the one it replaces.If you need to replace any of your wheels, wheel
bolts or wheel nuts, replace them only with
new GM original equipment parts. This way, you
will be sure to have the right wheel, wheel
bolts and wheel nuts for your vehicle.
{CAUTION:
A leaking wheel could fail without warning.
A wheel designed for tubeless tires could
be leaking because it is damaged. Do not
use an inner tube or some other thing to try
to stop the leaking. Get a new wheel of the
proper type.
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