1999 GMC SIERRA suspension

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4-26 Driving in Water
Light rain causes no special off-road driving problems.
But heavy rain can mean flash flooding, and flood
waters demand extreme caution.
Find out how deep the water is before you drive through
it. If it's deep enough to cover your wheel hubs, axles or
exhaust pipe, don't try it
-- you probably won't get
through. Also, water that deep can damage your axle
and other vehicle parts.
If the water isn't too deep, then drive through it slowly.
At fast speeds, water splashes on your ignition system
and your vehicle can stall. Stalling can also occur if you
get your tailpipe under water. And, as long as your
tailpipe is under water, you'll never be able to start your
engine. When you go through water, remember that when
your brakes get wet, it may take you longer to stop.
CAUTION:
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it's
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Don't drive
through rushing water.
See ªDriving Through Waterº in the Index for more
information on driving through water.
After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust system
for damage. Also, check the fuel lines and cooling
system for any leakage.

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4-44
Using heavier suspension components to get added
durability might not change your weight ratings. Ask
your dealer to help you load your vehicle the right way.
NOTICE:
Some vehicles may be equipped with RPO VYU
(snow plow prep package). With this option, the
payload your vehicle can carry is reduced when a
snow plow is installed. Your vehicle can be
damaged if either the front or rear axle ratings,
or the GVW are exceeded.
As a general guideline, with a 650 lb. (295 kg)
snow plow, the weight of the occupants and cargo
must not exceed 300 lb. (135 kg). However, this
may depend on the vehicle's option content.
Therefore, to help avoid vehicle damage:

Make sure the weight on the front andrear
axles does not exceed their respective
axle ratings.
NOTICE: (Continued)
NOTICE: (Continued)

For the front axle, if more cargo or
passengers need to be carried, appropriate
counter ballast must be installed rear of the
rear axle and properly secured.

Total vehicle weight must not exceed the
GVW rating.

See your dealer for advice and information
about using a snow plow on your vehicle.
CAUTION:
Do not load your vehicle any heavier than the
GVWR, or either the maximum front or rear
GAWR. If you do, parts on your vehicle can
break, and it can change the way your vehicle
handles. These could cause you to lose control
and crash. Also, overloading can shorten the life
of your vehicle.

Short Trip/City Scheduled Maintenance -- Gasoline Engines
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7-8
The services shown in this schedule up to 100,000 miles
(166 000 km) should be performed after 100,000 miles
(166 000 km) at the same intervals. The services shown
at 150,000 miles (240 000 km) should be performed at
the same interval after 150,000 miles (240 000 km).
See ªOwner Checks and Servicesº and ªPeriodic
Maintenance Inspectionsº following.
Footnotes

The U.S. Environmental Protection Agency or the
California Air Resources Board has determined that the
failure to perform this maintenance item will not nullify
the emission warranty or limit recall liability prior to the
completion of the vehicle's useful life. We, however,
urge that all recommended maintenance services be
performed at the indicated intervals and the maintenance
be recorded.# Lubricate the front suspension, kingpin bushings,
steering linkage, transmission shift linkage, transfer case
shift linkage, parking brake cable guides, rear driveline
center splines, front axle propshaft spline and brake
pedal springs. Ball joints and kingpin bushings should
not be lubricated unless their temperature is 10F
(
-12C) or higher, or they could be damaged.
+ A good time to check your brakes is during tire
rotation. See ªBrake System Inspectionº under ªPeriodic
Maintenance Inspectionsº in Part C of this schedule.

Long Trip/Highway Scheduled Maintenance -- Gasoline Engines
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7-30
The services shown in this schedule up to 100,000 miles
(166 000 km) should be performed after 100,000 miles
(166 000 km) at the same intervals. The services shown
at 150,000 miles (240 000 km) should be performed at
the same interval after 150,000 miles (240 000 km).
See ªOwner Checks and Servicesº and ªPeriodic
Maintenance Inspectionsº following.
Footnotes
 The U.S. Environmental Protection Agency or the
California Air Resources Board has determined that the
failure to perform this maintenance item will not nullify
the emission warranty or limit recall liability prior to the
completion of the vehicle's useful life. We, however,
urge that all recommended maintenance services be
performed at the indicated intervals and the maintenance
be recorded.
# Lubricate the front suspension, kingpin bushings,
steering linkage, transmission shift linkage, transfer case
shift linkage, parking brake cable guides, rear drivelinecenter splines, front axle propshaft spline and brake
pedal springs. Ball joints and kingpin bushings should
not be lubricated unless their temperature is 10F
(
-12C) or higher, or they could be damaged.
+ A good time to check your brakes is during tire
rotation. See ªBrake System Inspectionº under ªPeriodic
Maintenance Inspectionsº in Part C of this schedule.
** Drive axle service (see ªRecommended Fluids and
Lubricantsº in the Index for proper lubricant to use):

Check fluid level and add fluid as needed.

If your vehicle has a locking differential, drain fluid
and refill at first engine oil change.

3500 HD Models with applications requiring
high
-speed (above 45 mph or 70 km/h) operation for
extended periods of time must have the drive axle
fluid changed every 30,000 miles (50 000 km).

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7-46
Part C: Periodic Maintenance
Inspections
Listed in this part are inspections and services which
should be performed at least twice a year (for instance,
each spring and fall). You should let your dealer's
service department or other qualified service center do
these jobs. Make sure any necessary repairs are
completed at once.
Proper procedures to perform these services may be
found in a service manual. See ªService and Owner
Publicationsº in the Index.
Steering and Suspension Inspection
Inspect the front and rear suspension and steering
system for damaged, loose or missing parts, signs of
wear or lack of lubrication. Inspect the power steering
lines and hoses for proper hook
-up, binding, leaks,
cracks, chafing, etc.
Exhaust System Inspection
Inspect the complete exhaust system. Inspect the body
near the exhaust system. Look for broken, damaged,
missing or out
-of-position parts as well as open seams,
holes, loose connections or other conditions which could
cause a heat build
-up in the floor pan or could let
exhaust fumes into the vehicle. See ªEngine Exhaustº in
the Index.
Engine Cooling System Inspection
Inspect the hoses and have them replaced if they are
cracked, swollen or deteriorated. Inspect all pipes,
fittings and clamps; replace as needed. Clean the outside
of the radiator and air conditioning condenser. To help
ensure proper operation, a pressure test of the cooling
system and pressure cap is recommended at least once
a year.

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8-12
CURRENT PUBLICATIONS FOR 1999 GMC
SERVICE MANUALS
Service Manuals have the diagnosis and repair information
on engines, transmission, axle, suspension, brakes,
electrical, steering, body, etc.
RETAIL SELL PRICE: $90.00
TRANSMISSION, TRANSAXLE, TRANSFER CASE
UNIT REPAIR MANUAL
This manual provides information on unit repair service
procedures, adjustments and specifications for the
1999 GM transmissions, transaxles and transfer cases.
RETAIL SELL PRICE: $50.00
SERVICE BULLETINS
Service Bulletins give technical service information needed
to knowledgeably service General Motors cars and trucks.
Each bulletin contains instructions to assist in the
diagnosis and service of your vehicle.OWNER'S INFORMATION
Owner publications are written directly for Owners and
intended to provide basic operational information about the
vehicle. The owner's manual will include the Maintenance
Schedule for all models.
In-Portfolio: Includes a Portfolio, Owner's Manual and
Warranty Booklet.
RETAIL SELL PRICE: $20.00
Without Portfolio: Owner's Manual only.
RETAIL SELL PRICE: $15.00
CURRENT & PAST MODEL ORDER FORMS
Service Publications are available for current and past
model GM vehicles. To request an order form, please
specify year and model name of the vehicle.
PLEASE COMPLETE THE ORDER FORM SHOWN ON
THE FOLLOWING PAGE AND MAIL TO:
Helm, Incorporated
P.O. Box 07130
Detroit, MI 48207OR ORDER TOLL FREE: 1-800-551-4123
Monday-Friday 8:00 AM ± 6:00 PM Eastern Time
For Credit Card Orders Only (VISA±MasterCard±Discover)
1999 GMC SERVICE PUBLICATIONS ORDERING INFORMATION
The following publications covering the operation and servicing of your vehicle can be purchased by filling out
the Service Publication Order Form in this book and mailing it in with your check, money order,
or credit card information to Helm, Incorporated (address below.)

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9-5
Gages
Engine Coolant Temperature 2-69 . . . . . . . . . . . . . . . . . . . .
Engine Oil Pressure 2-72 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel 2-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Speedometer 2-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tachometer 2-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltmeter 2-67 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Garage Door Opener 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GAWR 4-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gear Positions, Automatic Transmission 2-16 . . . . . . . . . . . . .
Gear Positions, Manual Transmission 2-19, 2-20 . . . . . . . . . .
Glove Box 2-50 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GM Mobility Program for Persons with Disabilities 8-5 . . . . .
GM Vehicle Care/Appearance Materials 6-68 . . . . . . . . . . . . .
Gross Axle Weight Rating 4-43 . . . . . . . . . . . . . . . . . . . . . . . .
Gross Vehicle Weight Rating 4-43 . . . . . . . . . . . . . . . . . . . . . .
Guide en Fran†ais ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GVWR 4
-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Halogen Bulbs 6-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hazard Warning Flashers 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . .
Head Restraints 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamps 2-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bulb Replacement 6-39, 6-40 . . . . . . . . . . . . . . . . . . . . . . .
High/Low Beam Changer 2-36 . . . . . . . . . . . . . . . . . . . . . .
On Reminder 2-41 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring 6-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hearing Impaired, Customer Assistance 8-4 . . . . . . . . . . . . . .
Heating 3-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High-Beam Headlamps 2-36 . . . . . . . . . . . . . . . . . . . . . . . . . .
Highway Hypnosis 4-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hill and Mountain Roads 4
-34 . . . . . . . . . . . . . . . . . . . . . . . . .
Hitches, Trailer 4-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hood
Checking Things Under 6
-8 . . . . . . . . . . . . . . . . . . . . . . . . .
Release 6-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Horn 2-35 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydraulic Clutch Fluid 6-24, 7-48 . . . . . . . . . . . . . . . . . . . . . .
Hydraulic Clutch System Check 7-42 . . . . . . . . . . . . . . . . . . .
Hydroplaning 4-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Positions 2-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Transmission Lock Check 7-44 . . . . . . . . . . . . . . . . .
Illuminated Entry 2-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inflation, Tire 6-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inside Day/Night Rearview Mirror 2-44 . . . . . . . . . . . . . . . . .
Inspections 7-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake System 7-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drive Axle 7-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust Systems 7-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Radiator and Heater Hose 7-46 . . . . . . . . . . . . . . . . . . . . . .
Steering 7-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Suspension 7-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Throttle Linkage 7-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transfer Case (Four-Wheel Drive) 7-47 . . . . . . . . . . . . . . .
Instrument Panel 2-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cluster 2-62 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block 6-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Intensity Control 2-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interior Lamps 2-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .