
For driving with a trailer, the yellow and red, if equipped,
knobs must be pushed in. When you are not pulling a
trailer, the red trailer air supply knob must be pulled out.
{CAUTION:
If you apply any one of the air brake parking
controls while the vehicle is moving, your rig
will stop suddenly. If you are not ready for this,
you or others could be injured. Do not apply any
one of these controls while you are driving,
unless you have to make an emergency stop.
If the air pressure drops below 60 to 70 psi
(413 to 482 kPa), the primary brake light and warning
buzzer will come on. If the air pressure drops to
35 to 45 psi (241 to 310 kPa), the red trailer air supply
knob will automatically pop out and apply the spring
brakes on the trailer.
If the air pressure drops to 35 to 45 psi (241 to 310 kPa),
the yellow park brake knob will automatically pop out
and apply the spring brakes on the truck or tractor.
If you ever have a complete loss of air so that your air
brakes automatically apply, there is a way that the
tow operator can release the parking brakes to tow the
vehicle. SeeTowing Your Vehicle on page 4-37.
Air Suspension
Your vehicle may have the Hendrickson HAS Series
single-axle air suspension which is designed for a
single-axle on-highway use. This feature is available in
19,000 lb (8 613.3 kg), 21,000 lb (9 525.4 kg) and
23,000 lb (10 432.6 kg) capacities.
Rear Air Suspension Dump Control
If your vehicle is equipped with the Hendrickson HAS
Series single-axle air suspension, you may have
this control. The air suspension dump control allows the
operator to lower the deck height approximately
4.5 inches (11.5 cm) from the normal frame height.
The switch to deflate and
inflate the air suspension
is located in the instrument
panel.
Press the bottom of the switch to deflate the air
suspension and lower the deck height. Press the top of
the switch to return the suspension to normal deck height.
An indicator light will come on and stay on whenever
the switch is in the dumped position.
2-44

Four-Wheel Disc Brakes
(Hydraulic Only)
Your vehicle has four-wheel disc brakes.
Some driving conditions or climates may cause a brake
squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
your brakes.
Brake linings should always be replaced as complete
axle sets.
Four-Wheel and Six-Wheel Drum
Brakes (Air Only)
The brake drums should be removed and inspected
each time the tires are removed for rotation or changing.
When you have the front brakes replaced, have the
rear brakes inspected, too.
Brake linings should always be replaced as complete
axle sets.
Brake Pedal Travel
See your dealer if the brake pedal does not return to
normal height, or if there is a rapid increase in
pedal travel. This could be a sign of brake trouble.
Brake Adjustment
Every time you make a brake stop, your brakes adjust
for wear.
Replacing Brake System Parts
The braking system on a vehicle is complex. Its many
parts have to be of top quality and work well together
if the vehicle is to have really good braking. Your
vehicle was designed and tested with top-quality
GM brake parts. When you replace parts of your braking
system — for example, when your brake linings wear
down and you need new ones put in — be sure you get
new approved GM replacement parts. If you do not,
your brakes may no longer work properly. For example,
if someone puts in brake linings that are wrong for
your vehicle, the balance between your front and rear
brakes can change — for the worse. The braking
performance you have come to expect can change in
many other ways if someone puts in the wrong
replacement brake parts.
5-51

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 or the proper type.
{CAUTION:
Without the correct wheel, you may not be able
to stop properly, and you could have other
problems like a tire air-out. You could have a
collision. If you do not go to your dealer to get
a new wheel, be sure you get the correct one.
Each new wheel should match the original
wheel in load-carrying capacity, in ation
pressure capacity, diameter, width, offset and
mounting con guration.
Using wheels and tires with higher load-carrying limits
than the original wheels and tires does not change
the Gross Axle Weight Rating (GAWR) or the Gross
Vehicle Weight Rating (GVWR) of your vehicle.
SeeLoading Your Vehicle on page 4-34for more
information.
Notice:The wrong wheel can cause trouble in
bearing life, brake cooling, speedometer/odometer
calibration, headlamp aim, bumper height, vehicle
ground clearance, stopping distance and tire
clearance to the body and chassis. You could also
have other problems like a tire air-out.
5-81

Range Inhibit Warning Indicator........................3-33
Reading Lamps..............................................3-17
Rear Axle......................................................5-64
Differential Lock Control...............................4-11
Shift Motor.................................................5-65
Two-Speed Electric Shift Control....................2-28
Rear Heating System......................................3-24
Rear Outside Passenger Positions, Safety Belts....1-25
Rear Seat Operation......................................... 1-8
Rearview Mirrors.............................................2-47
Reduced Engine Power Light............................3-42
Remote Keyless Entry System............................ 2-3
Remote Keyless Entry System, Operation............ 2-4
Reporting Safety Defects
Canadian Government..................................7-11
General Motors...........................................7-11
United States Government............................7-10
Restraint System Check
Checking the Restraint Systems....................1-62
Replacing Restraint System Parts
After a Crash..........................................1-63
Right Front Passenger Position, Safety Belts......1-23
Roadside
Assistance Program....................................... 7-5
Rocking Your Vehicle to Get it Out....................4-32
Running Out of Fuel........................................5-17
Running the Engine While Parked.....................2-46S
Safety Belt
Reminder Light............................................3-28
Reminder Tone............................................3-28
Safety Belts
Care of ......................................................5-86
Center Passenger Position............................1-24
Driver Position............................................1-15
How to Wear Safety Belts Properly................1-14
Questions and Answers About Safety Belts.....1-14
Rear Outside Passenger Positions.................1-25
Right Front Passenger Position......................1-23
Safety Belt Extender....................................1-28
Safety Belt Use During Pregnancy.................1-23
Safety Belts Are for Everyone......................... 1-9
Shoulder Belt Height Adjuster........................1-22
Safety Warnings and Symbols.............................. iii
Scheduled Maintenance..................................... 6-5
Scheduled Maintenance Supplements.................. 6-4
Seats
Air Suspension Seats.................................... 1-6
Bucket Seats................................................ 1-2
Rear Seat Operation...................................... 1-8
Split Bench Seat........................................... 1-6
11

Securing a Child Restraint
Center Rear Seat Position (Crew Cab)
or Center Front Position............................1-44
Rear Outside Seat Position...........................1-42
Right Front Seat Position..............................1-46
Service........................................................... 5-3
California Proposition 65 Warning.................... 5-3
Doing Your Own Work................................... 5-4
Engine Fan Breakage.................................... 5-5
Engine Soon Light.......................................3-38
Publications Ordering Information...................7-11
Transmission Warning Light..........................3-32
Servicing Your Airbag-Equipped Vehicle..............1-61
Setting the Time.............................................3-49
Sheet Metal Damage.......................................5-89
Shoulder Belt Height Adjuster...........................1-22
Signals, Turn and Lane-Change.......................... 3-8
Sliding Rear Windows.....................................2-10
Snow Plow....................................................4-36
Specifications, Capacities.................................5-99
Speedometer..................................................3-27
Split Bench Seat.............................................. 1-6
Starting Your Diesel Engine..............................2-15
Starting Your Gasoline Engine..........................2-13
Steering........................................................4-13
Steering Wheel, Tilt Wheel................................. 3-7Storage Areas................................................2-49
Center Console Storage Area........................2-49
Stuck in Sand, Mud, Ice, or Snow.....................4-32
Sun Visors.....................................................2-10
Suspension, Air..............................................2-44
Switchbanks, Instrument Panel..........................3-18
T
Tachometer....................................................3-27
Theft-Deterrent, Radio.....................................3-64
Tilt Wheel........................................................ 3-7
Tires.............................................................5-74
Aluminum or Chrome-Plated Wheels,
Cleaning.................................................5-89
Cleaning....................................................5-89
Dual Tire Operation.....................................5-76
If a Tire Goes Flat.......................................5-82
Inflation - Tire Pressure................................5-75
Tightening the Wheel Nuts............................5-77
Wheel Alignment and Tire Balance.................5-77
Wheel Loading............................................5-75
Wheel Replacement.....................................5-81
When It Is Time for New Tires......................5-76
Tow Hooks.....................................................4-33
12