1999 CHEVROLET SILVERADO four wheel drive

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6-25
Rear Axle
When to Check Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant. See ªScheduled
Maintenance Servicesº in the Index.
How to Check Lubricant
1500 Series shown, 2500 Series similarThe proper level for the 1500 Series is from 5/8 inch
to 1 5/8 inch (15 mm to 40 mm) below the filler plug.
The proper level for the 2500 Series is from 0 to
3/8 inch (0 to 10 mm) below the filler plug. Add only
enough fluid to reach the proper level.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See ªRecommended Fluids and
Lubricantsº in the Index.
Four-Wheel Drive
Most lubricant checks in this section also apply to
four
-wheel-drive vehicles. However, they have two
additional systems that need lubrication.

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6-36
NOTICE:

Using the wrong fluid can badly damage
brake system parts. For example, just a few
drops of mineral
-based oil, such as engine
oil, in your brake system can damage brake
system parts so badly that they'll have to be
replaced. Don't let someone put in the
wrong kind of fluid.

If you spill brake fluid on your vehicle's
painted surfaces, the paint finish can be
damaged. Be careful not to spill brake fluid
on your vehicle. If you do, wash it off
immediately. See ªAppearance Careº in
the Index.
Brake Wear
Your vehicle has four-wheel disc brakes.
Disc brake pads have built
-in wear indicators that make a
high
-pitched warning sound when the brake pads are worn
and new pads are needed. The sound may come and go or
be heard all the time your vehicle is moving (except when
you are pushing on the brake pedal firmly).
CAUTION:
The brake wear warning sound means that soon
your brakes won't work well. That could lead to
an accident. When you hear the brake wear
warning sound, have your vehicle serviced.
NOTICE:
Continuing to drive with worn-out brake pads
could result in costly brake repair.

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6-66
NAME Usage
L BODY Retained Accessory Power Relay
LOCK Power Door Locks
DRV UNLOCK Power Door Lock RelayNAME Usage
LOCK Power Door Lock Relay
HVAC 1 Climate Control System
CRUISE Cruise Control, Instrument Cluster
IGN 3 Ignition, Power Seats
4WD Four
-Wheel Drive System,
Auxiliary Battery
CRANK Starting System
INT PRK Parking Lamps, Sidemarker
Lamps, Interior Lamps
L DOOR Power Door Lock Relay
BRAKE Anti
-Lock Brake System
RR WIPER Not Used
ILLUM Interior Lamps
SEAT Power Seat Circuit Breaker

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7-4
Part A: Scheduled Maintenance
Services
Using Your Maintenance Schedule
We at General Motors want to help you keep your
vehicle in good working condition. But we don't know
exactly how you'll drive it. You may drive very short
distances only a few times a week. Or you may drive
long distances all the time in very hot, dusty weather.
You may use your vehicle in making deliveries. Or
you may drive it to work, to do errands or in many
other ways.
Because of all the different ways people use their
vehicles, maintenance needs vary. You may need more
frequent checks and replacements. So please read the
following and note how you drive. If you have any
questions on how to keep your vehicle in good
condition, see your dealer.
This part tells you the maintenance services you should
have done and when you should schedule them. If you
go to your dealer for your service needs, you'll know
that GM
-trained and supported service people will
perform the work using genuine GM parts.The proper fluids and lubricants to use are listed in
Part D. Make sure whoever services your vehicle uses
these. All parts should be replaced and all necessary
repairs done before you or anyone else drives
the vehicle.
This schedule is for vehicles that:

carry passengers and cargo within recommended
limits. You will find these limits on your vehicle's
Certification/Tire label. See ªLoading Your Vehicleº
in the Index.

are driven on reasonable road surfaces within legal
driving limits.

are driven off
-road in the recommended manner.
See ªOff
-Road Driving With Your
Four
-Wheel-Drive Vehicleº in the Index.

use the recommended fuel. See ªFuelº in the Index.

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7-24 Throttle System Inspection
Inspect the throttle system for interference or binding,
and for damaged or missing parts. Replace parts as
needed. Replace any components that have high effort
or excessive wear. Do not lubricate accelerator and
cruise control cables.
Drive Axle Service
Check rear/front axle fluid level and add as needed.
Check constant velocity joints and axle seals for leaking.
Transfer Case (Four-Wheel Drive)
Inspection
Every 12 months or at oil change intervals, check front
axle and transfer case and add lubricant when necessary.
On manual shift transfer case, oil the control lever pivot
point. Check vent hose at transfer case for kinks and
proper installation. More frequent lubrication may be
required on off
-road use.
Brake System Inspection
Inspect the complete system. Inspect brake lines and
hoses for proper hook
-up, binding, leaks, cracks,
chafing, etc. Inspect disc brake pads for wear and rotors
for surface condition. Inspect other brake parts,
including calipers, parking brake, etc. You may need to
have your brakes inspected more often if your driving
habits or conditions result in frequent braking.

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9-4
Driving (Continued)
Through Water 4-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wet Roads 4-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Winter 4-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
With a Trailer 4-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drunken Driving 4-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Easy Entry Seat 1-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Equipment, Adding 2-17, 3-26, 6-70 . . . . . . . . . . .
Electrical System 6-64 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrochromic Day/Night Rearview Mirror 2-56 . . . . . . . . . .
Engine 6-10, 6-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant 6-29, 6-75, 7-25 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Heater 2-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Level Check 7-18 . . . . . . . . . . . . . . . . . . . . . . . . . .
Coolant Temperature Gage 2-75 . . . . . . . . . . . . . . . . . . . . .
Cooling System Capacity 6-75 . . . . . . . . . . . . . . . . . . . . . . .
Exhaust 2-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block 6-69 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Identification 6-63 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oil Level Check 7-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overheating 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Running While Parked 2-40 . . . . . . . . . . . . . . . . . . . . . . . . .
Specifications 6-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Starting Your 2-16, 2-18 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Underhood Electrical Center 6-69 . . . . . . . . . . . . . . . . . . . .
Engine Fan Noise 5-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Oil 6-12, 7-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding 6-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Additives 6-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking 6-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oil Life Monitor 6
-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Gage 2-79 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Used 6-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
When to Change 6-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Overheated Message 2-85 . . . . . . . . . . . . . . . . . . . . . .
Exhaust, Engine 2-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fabric Cleaning 6-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fan Control, Climate Control System 3-2, 3-3 . . . . . . . . . . . .
Filling a Portable Fuel Container 6-8 . . . . . . . . . . . . . . . . . . . .
Filling Your Tank 6-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Filter
Engine Air Cleaner 6
-16, 6-77 . . . . . . . . . . . . . . . . . . . . . . .
Oil 6-77 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Passenger Compartment Air 3-5, 6-18, 6-77 . . . . . . . . . . .
Finish Care 6-58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Finish Damage 6-60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Flashers, Hazard Warning 5-2 . . . . . . . . . . . . . . . . . . . . . . . . .
Flat Tire, Changing 5-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid Capacities 6-75 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluids and Lubricants 7-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fog Lamps 2-53 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Foreign Countries, Fuel 6-5 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Four-Wheel Drive 2-27, 6-26 . . . . . . . . . . . . . . . . . . . . . . . . .
French Language Manual ii. . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle 6
-27, 7-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Axle Locking Feature 2-27 . . . . . . . . . . . . . . . . . . . . . . .
Front Axle Reserve Capacity 4-49 . . . . . . . . . . . . . . . . . . . . . .
Front Sidemarker Lamp Bulb Replacement 6-40 . . . . . . . . . . .
Front Towing 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Front Turn Signal Lamp Bulb Replacement 6-40 . . . . . . . . . .

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9-6
Inspections (Continued)
Steering 7-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Suspension 7-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Throttle System 7-24 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transfer Case (Four-Wheel Drive) 7-24 . . . . . . . . . . . . . . .
Instrument Panel 2-66 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cluster 2-66 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block 6-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Intensity Control 2-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jumper Wiring Harness 4-69 . . . . . . . . . . . . . . . . . . . . . . . .
Interior Lamps 2-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jack, Tire 5-22 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jump Starting 5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Key Lock Cylinders Service 7-20 . . . . . . . . . . . . . . . . . . . . .
Key Release Button 2-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keyless Entry System 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keys 2-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Labels
Certification 4-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Certification/Tire 4-46 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Parts Identification 6-63 . . . . . . . . . . . . . . . . . . . . .
Vehicle Identification Number 6-63 . . . . . . . . . . . . . . . . . . .
Lamps 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cargo 2-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-58 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dome 2-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exterior 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interior 2
-54 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
On Reminder 2-52 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Latches, Seatback 1-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Leaving Your Vehicle with the Engine Running 2-36 . . . . . . .
Lighter 2-64 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lights
4WD 2
-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Bag Off 1-33, 2-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Bag Readiness 1-27, 2-71 . . . . . . . . . . . . . . . . . . . . . . .
Anti-Lock Brake System Warning 2-74, 4-7 . . . . . . . . . . . .
Brake System Warning 2-74 . . . . . . . . . . . . . . . . . . . . . . . . .
Cruise 2-80 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safety Belt Reminder 1-12, 2-70 . . . . . . . . . . . . . . . . . . . . .
Service Engine Soon 2-77 . . . . . . . . . . . . . . . . . . . . . . . . . .
Shift 2-27, 2-73 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tow/Haul 2-81 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loading Information, Truck-Camper 4-50 . . . . . . . . . . . . . . .
Loading Your Vehicle 4-46 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loading Your Vehicle for Off-Road Driving 4-17 . . . . . . . . . .
Lockout Prevention 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Locks
Cylinders 7
-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Door 2-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Transmission Check 7-22 . . . . . . . . . . . . . . . . . . . .
Key Lock Cylinders Service 7-20 . . . . . . . . . . . . . . . . . . . .
Power Door 2-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Coolant Message 2-84, 6-31 . . . . . . . . . . . . . . . . . . . . . .
Low Fuel Message 2-87 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low Washer Fluid Message 2-87 . . . . . . . . . . . . . . . . . . . . . . .
Lubricants and Fluids 7-25 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lubrication Service, Body 7-20 . . . . . . . . . . . . . . . . . . . . . . . .
Lumbar Controls, Manual 1-3 . . . . . . . . . . . . . . . . . . . . . . . . .
Lumbar Controls, Power 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . .