1999 GMC C-SERIES wheel

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5-13
A. Hardwood Board
B. Swing Arm
5. Raise the vehicle to the required height.Single Drive Rear Axle
Disconnect the propshaft at the rear axle. Secure the
propshaft to the frame or crossmember.
Tandem Drive Rear Axles
-- Forward Axle Off
the Ground
Raise the front of the vehicle until the forward
tandem axle wheels are off the ground. Remove the
rearward propshaft.
Tandem Drive Rear Axle
-- Both Axles on the
Ground Due to Type of Suspension or Attached Load
Disconnect the propshaft at the forward tandem axle.
Secure the propshaft to the frame or crossmember.
If there is damage or suspected damage to the axle(s),
remove all axle shafts. Cover the hub openings to
prevent the loss of lubricant or entry of dirt or
foreign objects.
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5-14
After Towing
Block the rear wheels and install axle and propeller
shafts. Check for proper phasing of universal joints.
Apply the emergency brake system before disconnecting
from the towing vehicle. Check and fill the rear axle
with oil as required.
Towing Your Vehicle From the Front
(All Wheels On the Ground)
Your vehicle may be towed on all wheels provided the
steering is working. Remember that the power brakes
and power steering will not have power assist. Vehicles
with air brakes will not have brakes. There must be a
tow bar installed between the towing vehicle and the
disabled vehicle.
Before Towing
Block the wheels of the disabled vehicle. On vehicles
with air brakes, release the emergency brake system by
compressing the brake chamber springs as outlined in
this section. (Note: This is to prevent the possibility of
the emergency brake being applied during towing.)On vehicles with hydraulic brakes, release the
parking brake fully by moving the lever to the
fully
-released position.
On vehicles equipped with an electric/hydraulic parking
brake, remove the propshaft.
Disconnect the propshaft at the rear axle (forward axle
on tandem axle models). Secure the propshaft to the
frame or crossmember.
If there is damage or suspected damage to the axle(s),
remove the axle shafts. Cover the hub openings to
prevent the loss of lubricant or entry of dirt or
foreign objects.
After Towing
Block the rear wheels and install axle and propshafts.
Check for proper phasing of universal joints. Apply
the parking brake system before disconnecting from
the towing vehicle. Check and fill rear axle with oil
as required.
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5-15 Towing Your Vehicle From the Rear
(Rear Wheels Off the Ground)
Before Towing
Secure the steering wheel to maintain a straight
-ahead
position. Make certain that the front axle is not loaded
above the front axle Gross Axle Weight Rating (GAWR)
as indicated on the vehicle's Certification/Tire label.
After Towing
Block the rear wheels and release the steering. Apply the
parking brake system before disconnecting from the
towing vehicle.
Refer to the transmission shift label for
additional information.
Releasing Air-Operated Parking Brakes
If your vehicle has air brakes, you could have a special
towing problem. If your vehicle has to be towed because
you had a complete loss of air pressure from both
systems, the parking brakes may have applied. The tow
operator can release the brakes manually by using the
following steps. Then your vehicle can be towed with all
wheels or just the rear wheels on the ground.
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5-16
CAUTION:

Working on air brakes without first using
the release studs to compress the springs
can lead to injury. Never work on the air
brake chambers without first using the
release studs to compress the brake springs.

When the brake springs are manually
compressed, you will have no brakes.
Release your air
-operated parking brakes
manually only to tow the vehicle. Never
drive the vehicle with the brakes released.
1. Block the wheels of the vehicle.
2. Remove the release stud and nut from the side of the
brake chamber. Some chambers have studs which are
visible at all times.
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5-34
If a Tire Goes Flat
It's unusual for a tire to ªblow outº 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 ªblowout,º 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, the next part tells you what to do.
Changing a Flat Tire
A flat or damaged tire can be a major roadside problem.
You're very likely to have to go for help. Few drivers of
these vehicles have the necessary equipment aboard to
be able to change a flat tire safely. For example, youhave to have a truck jack that can lift several thousand
pounds and a torque wrench that can generate several
hundred foot
-pounds (newton-meters) of twisting force.
So if you're stopped somewhere by a flat or damaged
tire or wheel, you should get expert help right then.
If the correct equipment is available, though, here is the
procedure to follow.

Does the tire still seem to have air under pressure in
it? If so, stand to the side and look at the wheel. See
if it looks like another wheel on the vehicle. If so, go
on to the next step. If it doesn't, or even if you can't
be sure, stop and get expert help.
CAUTION:
Tire-rim assemblies can explode. If you work on
a pressurized tire mounted on a damaged wheel,
the assembly can expand with explosive force
without warning. You and others nearby can be
badly injured. Don't work around a tire that has
air under pressure in it when its wheel is or might
be damaged.
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5-35

If the wheel looks normal, see if the wheel has side
rings and a lock ring around the wheel rim. If so,
they must be seated properly. You can compare with
another wheel on the vehicle as you check for this.
For dual wheels, you have to look between the tires
to make this check. You may not be able to tell
if the side rings or lock rings are seated properly
by looking. If you can't be sure, stop and get
expert help.
CAUTION:
If you work on a pressurized tire mounted on a
damaged wheel, the assembly can expand with
explosive force without warning. You and others
nearby can be badly injured. Don't work around
a tire that has air under pressure in it when its
lock ring or side ring might not be
properly seated.
CAUTION:
Rust or dirt on the wheel, or on the parts to
which it is fastened, can make the wheel nuts
become loose after a time. The wheel could come
off and cause an accident. When you change a
wheel, remove any rust or dirt from the 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.

If the lock ring and side rings seem to be seated
properly (or if the wheel doesn't have these), let the
air out of the tire. You can do this by taking out the
valve core.

If the flat or damaged tire is one of a dual set, let the
air out of both tires of the dual before you take off
the damaged tire and rim assembly.

If you have the correct equipment, put on the spare
wheel and tire assembly.
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5-36
CAUTION:
Never use oil or grease on studs or nuts. If you
do, the nuts might come loose. Your wheel could
fall off, causing a serious accident.
CAUTION:

There are many ways to be hurt badly, or
be killed, while you are trying to change a
truck tire and rim. Follow all of the safety
precautions on the truck jack and
other equipment.
CAUTION: (Continued)
CAUTION: (Continued)

If you try to put air back into a tire that has
run flat, or even a tire that was quite low on
air, without first finding out why it was low
or flat, the tire can have a sudden air
-out.
This could cause you to lose control of the
vehicle and have a serious crash. Don't
refill a flat or very low tire with air without
first having the tire taken off the wheel and
checked for damage.

Use a clip-on chuck and hose extension when you
add air to your tires. You'll need an accurate truck
tire pressure gage. Stand to one side and add the air.
Be sure you don't go over the top inflation pressure
for the tire.
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5-37
CAUTION:
Incorrect wheel nuts or improperly tightened
wheel nuts can cause the wheel to become loose
and even come off. This could lead to an accident.
Be sure to use the correct wheel nuts. If you have
to replace them, be sure to get new GM original
equipment wheel nuts.
Stop somewhere as soon as you can and have the
nuts tightened with a torque wrench.
See ªTightening the Wheel Nutsº in the Index for
the proper torque for your particular wheel.
NOTICE:
Improperly tightened wheel nuts can lead to
brake pulsation and rotor damage. To avoid
expensive brake repairs, evenly tighten the wheel
nuts in the proper sequence and to the proper
torque specification.
If You're Stuck: In Sand, Mud,
Ice or Snow
In order to free your vehicle when it is stuck, you will
need to spin the wheels, but you don't want to spin your
wheels too fast. The method known as ªrockingº can
help you get out when you're stuck, but you must
use caution.
CAUTION:
If you let your tires spin at high speed, they can
explode, and you or others could be injured. And,
the transmission or other parts of the vehicle can
overheat. That could cause an engine
compartment fire or other damage. When you're
stuck, spin the wheels as little as possible. Don't
spin the wheels above 35 mph (55 km/h) as shown
on the speedometer.
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