1999 GMC Sierra Owners Manual

If the wheel also has a trim ring, use the wheel wrench to pry along the edge and remove it. If the wheel has a smooth center piece, place the wheel wrench in the slot on the wheel and gently pry out.

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Removing the Flat Tire and Installing the Spare Tire

1. Use the ratchet and

wheel wrench to loosen all the wheel nuts. Turn the wheel wrench counterclockwise, with DOWN facing you, to loosen the wheel nuts. Don’t remove the wheel nuts yet.

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2. Position the jack under the vehicle. If the flat tire is on the front of the vehicle, position the jack on the frame behind the flat tire. If the flat tire is on the rear, position the jack on the rear axle between the spring and the shock absorber.

CAUTION:

Getting under a vehicle when it is jacked up is dangerous. If the vehicle slips off the jack, you could be badly injured or killed. Never get under a vehicle when it is supported only by a jack.

CAUTION:

Raising your vehicle with the jack improperly positioned can damage the vehicle and even make the vehicle fall. To help avoid personal injury and vehicle damage, be sure to fit the jack lift head into the proper location before raising the vehicle.

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4. Remove all the wheel nuts and take off the flat tire.

Front Position

Rear Position

3. With UP on the ratchet facing you, raise the vehicle by rotating the ratchet and wheel wrench clockwise. Raise the vehicle far enough off the ground so there is enough room for the spare tire to fit.

5. Remove any rust or dirt

from the wheel bolts, mounting surfaces and spare wheel.

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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.

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.

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6. Replace the wheel

nuts with the rounded end of the nuts toward the wheel. Tighten each wheel nut by hand using the wheel wrench until the wheel is held against the hub.

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8. Tighten the nuts

firmly in a crisscross sequence as shown by rotating the wheel wrench clockwise.

Front Position

Rear Position

CAUTION:

7. Lower the vehicle by rotating the ratchet and wheel

wrench counterclockwise. Lower the jack completely.

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 to the proper torque. See “Capacities and Specifications” in the Index.

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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.

9. Put the wheel trim back on. For vehicles with plastic

wheel nut caps, tighten the caps until they are finger-tight, then tighten them an additional one-half of a turn with the ratchet and wheel wrench.

Storing a Flat or Spare Tire and Tools

CAUTION:

Storing a jack, a tire or other equipment in the passenger compartment of the vehicle could cause injury. In a sudden stop or collision, loose equipment could strike someone. Store all these in the proper place.

Store the flat tire where the spare tire was stored.

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For an underbody spare tire carrier, store the tire under the rear of the vehicle in the spare tire carrier. To store the tire: 1. Put the tire on the ground at the rear of the vehicle with the valve stem pointed down and to the rear. 2. Tilt the retainer downward and through the wheel opening. Make sure that the retainer is fully seated across the underside of the wheel.

3. Attach the ratchet, with the UP mark facing you,

near the hook at the end of the jack handle. Insert the other end, on an angle, through the hole in the rear bumper and into the hoist shaft.

4. Raise the tire fully against the underside of the

vehicle. Continue turning the ratchet until there are two “clicks” or “ratchets.” The spare tire hoist cannot be over-tightened.

5. Grasp and push against the tire to be sure it is stored

securely and does not move.

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A. Hoist Assembly B. Ratchet C. Jack Handle D. Hoist Shaft

E. Valve Stem,

Pointed Down

F. Flat or Spare Tire G. Retainer H. Hoist Cable

Return the jack, ratchet, wheel wrench and jack extensions to their location behind the passenger’s seat. Secure the items and replace the jack cover, if there is one.

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2 and 4-Door Models

A. Nut B. Jack C. Jack Handle Extension D. Wheel Wrench

E. Jack and Tool

Storage Box

F. Ratchet G. Jack Handle H. Tool Retainer

Extended Cab Models

A. Nut B. Jack and Tool Cover C. Jack Handle Extension D. Tool Retainer E. Jack and Tool

Storage Box

F. Ratchet G. Wheel Wrench H. Jack I.

Jack Handle

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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 “rocking” 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.

Chassis Cab Models

A. Nut B. Retainer C. Jack Handle

Extension

D. Jack Handle Extension E. Wheel Wrench

F. Jack and Tool

Storage Box

G. Ratchet H. Jack Handle I. Tool Retainer J. Jack

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NOTICE:

Spinning your wheels can destroy parts of your vehicle as well as the tires. If you spin the wheels too fast while shifting your transmission back and forth, you can destroy your transmission.

For information about using tire chains on your vehicle, see “Tire Chains” in the Index. Rocking Your Vehicle To Get It Out First, turn your steering wheel left and right. That will clear the area around your front wheels. If you have a four-wheel drive vehicle, shift into 4HI. Then shift back and forth between REVERSE (R) and a forward gear (or with a manual transmission, between FIRST (1) or SECOND (2) and REVERSE (R)), spinning the wheels as little as possible. Release the accelerator pedal while you shift, and press lightly on the accelerator pedal when the transmission is in gear. By slowly spinning your wheels in the forward and reverse directions, you will cause a rocking motion that may free your vehicle. If that doesn’t get you out after a few tries, you may need to be towed out. Or, you can use your recovery hooks if your vehicle has them. If you do need to be towed out, see “Towing Your Vehicle” in the Index.

Using the Recovery Hooks

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Your vehicle may be equipped with recovery hooks. The recovery hooks are provided at the front of your vehicle. You may need to use them if you’re stuck off-road and need to be pulled to some place where you can continue driving.

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CAUTION:

The recovery hooks, when used, are under a lot of force. Always pull the vehicle straight out. Never pull on the hooks at a sideways angle. The hooks could break off and you or others could be injured from the chain or cable snapping back.

NOTICE:

Never use the recovery hooks to tow the vehicle. Your vehicle could be damaged and it would not be covered by warranty.

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- NOTES

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- NOTES

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Section 6 Service and Appearance Care

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Here you will find information about the care of your vehicle. This section begins with service and fuel information, and then it shows how to check important fluid and lubricant levels. There is also technical information about your vehicle, and a part devoted to its appearance care.

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Service Fuel (Gasoline Engine) Fuels in Foreign Countries (Gasoline Engines) Filling Your Tank (Gasoline Engine) Filling a Portable Fuel Container Checking Things Under the Hood Noise Control System Engine Oil (Gasoline Engine) Engine Air Cleaner/Filter (Gasoline Engines) Automatic Transmission Fluid Manual Transmission Fluid Hydraulic Clutch Rear Axle Four-Wheel Drive Radiator Pressure Cap (Gasoline Engine) Thermostat Engine Coolant

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Power Steering Fluid Windshield Washer Fluid Brakes Battery Bulb Replacement Windshield Wiper Blade Replacement Tires Appearance Care Cleaning the Inside of Your Vehicle Cleaning the Outside of Your Vehicle GM Vehicle Care/Appearance Materials Vehicle Identification Number (VIN) Electrical System Replacement Bulbs Capacities and Specifications Air Conditioning Refrigerants Normal Maintenance Replacement Parts

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Service Your dealer knows your vehicle best and wants you to be happy with it. We hope you’ll go to your dealer for all your service needs. You’ll get genuine GM parts and GM-trained and supported service people. We hope you’ll want to keep your GM vehicle all GM. Genuine GM parts have one of these marks:

Doing Your Own Service Work If you want to do some of your own service work, you’ll want to use the proper service manual. It tells you much more about how to service your vehicle than this manual can. To order the proper service manual, see “Service and Owner Publications” in the Index. You should keep a record with all parts receipts and list the mileage and the date of any service work you perform. See “Maintenance Record” in the Index.

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CAUTION:

You can be injured and your vehicle could be damaged if you try to do service work on a vehicle without knowing enough about it. D Be sure you have sufficient knowledge,

experience, the proper replacement parts and tools before you attempt any vehicle maintenance task.

D Be sure to use the proper nuts, bolts and other fasteners. “English” and “metric” fasteners can be easily confused. If you use the wrong fasteners, parts can later break or fall off. You could be hurt.

Adding Equipment to the Outside of Your Vehicle Things you might add to the outside of your vehicle can affect the airflow around it. This may cause wind noise and affect windshield washer performance. Check with your dealer before adding equipment to the outside of your vehicle.

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Fuel (Gasoline Engine) If your vehicle has a diesel engine, see “Diesel Fuel Requirements and Fuel System” in the Diesel Engine Supplement. For vehicles with gasoline engines, please read this. Use regular unleaded gasoline rated at 87 octane or higher. It is recommended that the gasoline meet specifications which have been developed by the American Automobile Manufacturers Association (AAMA) and endorsed by the Canadian Motor Vehicle Manufacturers Association for better vehicle performance and engine protection. Gasolines meeting the AAMA specification could provide improved driveability and emission control system performance compared to other gasolines. For more information, write to: American Automobile Manufacturer’s Association, 7430 Second Ave, Suite 300, Detroit MI 48202. Be sure the posted octane is at least 87. If the octane is less than 87, you may get a heavy knocking noise when you drive. If it’s bad enough, it can damage your engine.

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If you’re using fuel rated at 87 octane or higher and you hear heavy knocking, your engine needs service. But don’t worry if you hear a little pinging noise when you’re accelerating or driving up a hill. That’s normal, and you don’t have to buy a higher octane fuel to get rid of pinging. It’s the heavy, constant knock that means you have a problem. If your vehicle is certified to meet California Emission Standards (indicated on the underhood emission control label), it is designed to operate on fuels that meet California specifications. If such fuels are not available in states adopting California emissions standards, your vehicle will operate satisfactorily on fuels meeting federal specifications, but emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn on and/or your vehicle may fail a smog-check test. (See “Malfunction Indicator Lamp” in the Index.) If this occurs, return to your authorized GM dealer for diagnosis to determine the cause of failure. In the event it is determined that the cause of the condition is the type of fuels used, repairs may not be covered by your warranty.

Some gasolines that are not reformulated for low emissions may contain an octane-enhancing additive called methylcyclopentadienyl manganese tricarbonyl (MMT); ask your service station operator whether or not his fuel contains MMT. General Motors does not recommend the use of such gasolines. If fuels containing MMT are used, spark plug life may be reduced and your emission control system performance may be affected. The malfunction indicator lamp on your instrument panel may turn on. If this occurs, return to your authorized GM dealer for service. To provide cleaner air, all gasolines in the United States are now required to contain additives that will help prevent deposits from forming in your engine and fuel system, allowing your emission control system to function properly. Therefore, you should not have to add anything to the fuel. In addition, gasolines containing oxygenates, such as ethers and ethanol, and reformulated gasolines may be available in your area to contribute to clean air. General Motors recommends that you use these gasolines, particularly if they comply with the specifications described earlier.

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You can also write us at the following address for advice. Just tell us where you’re going and give your Vehicle Identification Number (VIN).

General Motors Overseas Distribution Corporation 1908 Colonel Sam Drive Oshawa, Ontario L1H 8P7

Filling Your Tank (Gasoline Engine) If your vehicle has a diesel engine, see “Filling Your Tank (Diesel Engine)” in the Diesel Engine Supplement.

NOTICE:

Your vehicle was not designed for fuel that contains methanol. Don’t use it. It can corrode metal parts in your fuel system and also damage plastic and rubber parts. That damage wouldn’t be covered under your warranty.

Fuels in Foreign Countries (Gasoline Engines) If you plan on driving in another country outside the United States or Canada, the proper fuel may be hard to find. Never use leaded gasoline or any other fuel not recommended in the previous text on fuel. Costly repairs caused by use of improper fuel wouldn’t be covered by your warranty. To check on fuel availability, ask an auto club, or contact a major oil company that does business in the country where you’ll be driving.

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While refueling, let the cap hang by the tether below the fuel filler neck. To remove the cap, turn it slowly to the left (counterclockwise).

The fuel cap is located on the driver’s side of your vehicle. Refuel the front tank first on a chassis-cab model, or in instances when only a partial fuel fill is desired. An automatic transfer mechanism will maintain approximately equal fuel levels in both tanks, so no switching is required by the operator.

CAUTION:

Gasoline vapor is highly flammable. It burns violently, and that can cause very bad injuries. Don’t smoke if you’re near gasoline or refueling your vehicle. Keep sparks, flames and smoking materials away from gasoline.

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CAUTION:

If you get gasoline on yourself and then something ignites it, you could be badly burned. Gasoline can spray out on you if you open the fuel filler cap too quickly. This spray can happen if your tank is nearly full, and is more likely in hot weather. Open the fuel filler cap slowly and wait for any “hiss” noise to stop. Then unscrew the cap all the way.

Be careful not to spill gasoline. Clean gasoline from painted surfaces as soon as possible. See “Cleaning the Outside of Your Vehicle” in the Index.

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When you put the cap back on, turn it to the right (clockwise) until you hear a clicking sound. Make sure you fully install the cap. The diagnostic system can determine if the fuel cap has been left off or improperly installed. This would allow fuel to evaporate into the atmosphere. See “Malfunction Indicator Lamp” in the Index.

NOTICE:

If you need a new cap, be sure to get the right type. Your dealer can get one for you. If you get the wrong type, it may not fit properly. This may cause your malfunction indicator lamp to light and your fuel tank and emissions system may be damaged. See “Malfunction Indicator Lamp” in the Index.

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Filling a Portable Fuel Container

Checking Things Under the Hood

CAUTION:

CAUTION:

Never fill a portable fuel container while it is in your vehicle. Static electricity discharge from the container can ignite the gasoline vapor. You can be badly burned and your vehicle damaged if this occurs. To help avoid injury to you and others: D Dispense gasoline only into

approved containers.

D Do not fill a container while it is inside a

vehicle, in a vehicle’s trunk, pickup bed or on any surface other than the ground. D Bring the fill nozzle in contact with the

inside of the fill opening before operating the nozzle. Contact should be maintained until the filling is complete.

D Don’t smoke while pumping gasoline.

If your vehicle has air conditioning, the auxiliary engine fan under the hood can start up and injure you even when the engine is not running. Keep hands, clothing and tools away from any underhood electric fan.

CAUTION:

Things that burn can get on hot engine parts and start a fire. These include liquids like gasoline or diesel fuel, oil, coolant, brake fluid, windshield washer and other fluids, and plastic or rubber. You or others could be burned. Be careful not to drop or spill things that will burn onto a hot engine.

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Hood Release

To open the hood, first pull the handle inside the vehicle.

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Then go to the front of the vehicle and pull up on the secondary hood release, located just to the passenger’s side of the center of the grill. Lift the hood. Before closing the hood, be sure all filler caps are on properly. Pull down the hood and close it firmly.

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“VORTEC” 5000 and 5700 V8 Engine “VORTEC” 5700 engine shown, locations for other engines similar. When you lift up the hood you’ll see:

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A. Battery B. Engine Air Cleaner/Filter C. Radiator Cap D. Coolant Recovery Tank E. Air Filter Restriction Indicator F. Engine Oil Dipstick 6-10

G. Automatic Transmission

Dipstick (If Equipped)

H. Fan I. Power Steering Fluid Reservoir J. Engine Oil Fill K. Brake Fluid Reservoir

L. Clutch Fluid Reservoir

(If Equipped)

M. Windshield Washer Fluid

Reservoir

N. Fuse/Relay Center

“VORTEC” 7400 V8 Engine

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A. Battery B. Coolant Recovery Tank C. Engine Air Cleaner/Filter D. Radiator Cap E. Air Filter Restriction Indicator F. Engine Oil Dipstick

G. Automatic Transmission

Dipstick (If Equipped)

H. Engine Oil Fill I. Fan J. Power Steering Fluid Reservoir K. Brake Fluid Reservoir

L. Clutch Fluid Reservoir

(If Equipped)

M. Windshield Washer

Fluid Reservoir

N. Fuse/Relay Center

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Noise Control System The following information relates to compliance with Federal noise emission standards for vehicles with a Gross Vehicle Weight Rating (GVWR) of more than 10,000 lbs. (4 536 kg). The Maintenance Schedule provides information on maintaining the noise control system to minimize degradation of the noise emission control system during the life of your vehicle. The noise control system warranty is given in your Warranty booklet. These standards apply only to vehicles sold in the United States.

Tampering With Noise Control System Prohibited Federal law prohibits the following acts or the causing thereof: 1. The removal or rendering inoperative by any person,

other than for purposes of maintenance, repair or replacement, of any device or element of design incorporated into any new vehicle for the purpose of noise control, prior to its sale or delivery to the ultimate purchaser or while it is in use; or

2. The use of the vehicle after such device or element of design has been removed or rendered inoperative by any person.

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Among those acts presumed to constitute tampering are the acts listed below. Insulation: D Removal of the noise shields or any

underhood insulation.

Engine: D Removal or rendering engine speed governor

(if equipped) inoperative so as to allow engine speed to exceed manufacturer specifications.

Fan and Drive: D Removal of fan clutch (if equipped) or rendering

clutch inoperative.

D Removal of the fan shroud (if equipped). Air Intake: D Removal of the air cleaner silencer. D Reversing the air cleaner cover. Exhaust: D Removal of the muffler and/or resonator. D Removal of the exhaust pipes and exhaust

pipe clamps.

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Engine Oil (Gasoline Engine) If your vehicle has a diesel engine, see “Engine Oil (Diesel Engine)” in the Diesel Engine Supplement. It’s a good idea to check your engine oil every time you get fuel. In order to get an accurate reading, the oil must be warm and the vehicle must be on level ground.

The engine oil dipstick has a yellow ring handle and is located on the passenger’s side of the engine. Turn off the engine and give the oil several minutes to drain back into the oil pan. If you don’t, the oil dipstick might not show the actual level.

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Checking Engine Oil Pull out the dipstick and clean it with a paper towel or cloth, then push it back in all the way. Remove it again, keeping the tip down, and check the level.

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NOTICE:

Don’t add too much oil. If your engine has so much oil that the oil level gets above the upper mark that shows the proper operating range, your engine could be damaged.

The engine oil fill cap for the “VORTEC” 5000 and 5700 V8 engine is located on the driver’s side engine valve cover.

When to Add Engine Oil If the oil is at or below the ADD mark, then you’ll need to add at least one quart of oil. But you must use the right kind. This part explains what kind of oil to use. For crankcase capacity, see “Capacities and Specifications” in the Index.

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The engine oil fill cap for the “VORTEC” 7400 V8 engine is located at the front of the engine. Be sure to fill it enough to put the level somewhere in the proper operating range. Push the dipstick all the way back in when you’re through.

What Kind of Engine Oil to Use Oils recommended for your vehicle can be identified by looking for the “Starburst” symbol. This symbol indicates that the oil has been certified by the American Petroleum Institute (API). Do not use any oil which does not carry this Starburst symbol.

If you change your own oil, be sure you use oil that has the Starburst symbol on the front of the oil container.

If you have your oil changed for you, be sure the oil put into your engine is American Petroleum Institute certified for gasoline engines. You should also use the proper viscosity oil for your vehicle, as shown in the following chart:

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As shown in the chart, SAE 5W-30 is best for your vehicle. However, you can use SAE 10W-30 if it’s going to be 0_F (-18_C) or above. These numbers on an oil container show its viscosity, or thickness. Do not use other viscosity oils, such as SAE 20W-50.

NOTICE:

Use only engine oil with the American Petroleum Institute Certified For Gasoline Engines “Starburst” symbol. Failure to use the recommended oil can result in engine damage not covered by your warranty.

GM GoodwrenchR oil meets all the requirements for your vehicle. If you are in an area where the temperature falls below -20_F (-29_C), consider using either an SAE 5W-30
synthetic oil or an SAE 0W-30 oil. Both will provide easier cold starting and better protection for your engine at extremely low temperatures.

Engine Oil Additives Don’t add anything to your oil. Your dealer is ready to advise if you think something should be added. When to Change Engine Oil If any one of these is true for you, use the short trip/city maintenance schedule: D Most trips are less than 5 to 10 miles (8 to 16 km).

This is particularly important when outside temperatures are below freezing.

D Most trips include extensive idling (such as frequent

driving in stop-and-go traffic).

D You operate your vehicle in dusty areas or

off-road frequently.

D You frequently tow a trailer. D The vehicle is used for delivery service, police, taxi

or other commercial application.

Driving under these conditions causes engine oil to break down sooner. If any one of these is true for your vehicle, then you need to change your oil and filter every 3,000 miles (5 000 km) or 3 months -- whichever occurs first.

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If none of them is true, use the long trip/highway maintenance schedule. Change the oil and filter every 7,500 miles (12 500 km) or 12 months -- whichever occurs first. Driving a vehicle with a fully warmed engine under highway conditions causes engine oil to break down slower. What to Do with Used Oil Did you know that used engine oil contains certain elements that may be unhealthy for your skin and could even cause cancer? Don’t let used oil stay on your skin for very long. Clean your skin and nails with soap and water, or a good hand cleaner. Wash or properly throw away clothing or rags containing used engine oil. (See the manufacturer’s warnings about the use and disposal of oil products.) Used oil can be a real threat to the environment. If you change your own oil, be sure to drain all free-flowing oil from the filter before disposal. Don’t ever dispose of oil by putting it in the trash, pouring it on the ground, into sewers, or into streams or bodies of water. Instead, recycle it by taking it to a place that collects used oil. If you have a problem properly disposing of your used oil, ask your dealer, a service station or a local recycling center for help.

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Engine Air Cleaner/Filter (Gasoline Engines)

Your air cleaner is located between the battery and coolant recovery tank.

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The air cleaner assembly has an indicator that lets you know when the air filter is dirty and needs to be serviced. The indicator is located in the air intake tube between the air cleaner and the engine.

See “Owner Checks and Services” in the Index to determine when to check the indicator. If the area inside the clear section of the indicator is green, no air filter service is required. When the area inside the indicator is orange and CHANGE AIR FILTER appears, the filter should be replaced.

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To remove the air filter, unhook the retaining clips and remove the cover. Lift the filter and the connected duct out of the air cleaner housing. Hold the duct and remove the filter by both pulling and twisting the filter away from the duct. Care should be taken to dislodge as little dirt as possible. Clean the filter sealing surface of the duct and the filter housing. Install the new filter by pushing it all the way to the stop on the duct. Install the duct and the filter into the air cleaner housing. Make sure that the duct fits properly into the housing.

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CAUTION:

Operating the engine with the air cleaner/filter off can cause you or others to be burned. The air cleaner not only cleans the air, it stops flame if the engine backfires. If it isn’t there, and the engine backfires, you could be burned. Don’t drive with it off, and be careful working on the engine with the air cleaner/filter off.

Install the cover and fasten the two retaining clips. After the air filter is properly serviced, the indicator should be reset. Push the button on top of the indicator to reset it to the green (clean) filter zone. Refer to the Maintenance Schedule to determine when to replace the air filter. See “Owner Checks and Services” in the Index.

NOTICE:

If the air cleaner/filter is off, a backfire can cause a damaging engine fire. And, dirt can easily get into your engine, which will damage it. Always have the air cleaner/filter in place when you’re driving.

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Automatic Transmission Fluid If your vehicle has a diesel engine, see “Automatic Transmission Fluid” in the Diesel Supplement. When to Check and Change A good time to check your automatic transmission fluid level is when the engine oil is changed. Change both the fluid and filter every 50,000 miles (83 000 km) if the vehicle’s GVWR is over 8,600 or if the vehicle is mainly driven under one or more of these conditions: D In heavy city traffic where the outside temperature

regularly reaches 90_F (32_C) or higher.

D In hilly or mountainous terrain. D When doing frequent trailer towing. D Uses such as found in taxi, police or delivery service. If your vehicle’s GVWR is not over 8,600 and you do not use your vehicle under any of these conditions, change the fluid and filter every 100,000 miles (166 000 km). See “Scheduled Maintenance Services” in the Index.

How to Check Because this operation can be a little difficult, you may choose to have this done at the GM service department. If you do it yourself, be sure to follow all the instructions here, or you could get a false reading on the dipstick.

NOTICE:

Too much or too little fluid can damage your transmission. Too much can mean that some of the fluid could come out and fall on hot engine parts or exhaust system parts, starting a fire. Be sure to get an accurate reading if you check your transmission fluid.

Wait at least 30 minutes before checking the transmission fluid level if you have been driving: D When outside temperatures are above 90_F (32_C). D At high speed for quite a while. D In heavy traffic -- especially in hot weather. D While pulling a trailer.

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Checking the Fluid Level D Park your vehicle on a level place. Keep the

engine running.

D With the parking brake applied, place the shift lever

in PARK (P).

D With your foot on the brake pedal, move the shift lever through each gear range, pausing for about three seconds in each range. Then, position the shift lever in PARK (P).

D Let the engine run at idle for three minutes or more.

To get the right reading, the fluid should be at normal operating temperature, which is 180_F to 200_F (82_C to 93_C). Get the vehicle warmed up by driving about 15 miles (24 km) when outside temperatures are above 50_F (10_C). If it’s colder than 50_F (10_C), drive the vehicle in THIRD (3) until the engine temperature gage moves and then remains steady for 10 minutes. Then follow the hot check procedures.

Checking Transmission Fluid Cold A cold check is made after the vehicle has been sitting for eight hours or more with the engine off and is used only as a reference. Let the engine run at idle for five minutes if outside temperatures are 50_F (10_C) or more. If it’s colder than 50_F (10_C), you may have to idle the engine longer. Should the fluid level be low during a cold check, you must perform a hot check before adding fluid. This will give you a more accurate reading of the fluid level.

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Then, without shutting off the engine, follow these steps:

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3. Check both sides of the dipstick, and read the lower level. The fluid level must be in the COLD area for a cold check or in the HOT area or cross-hatched area for a hot check.

4. If the fluid level is in the acceptable range, push the

dipstick back in all the way; then flip the handle down to lock the dipstick in place.

1. The red transmission dipstick handle is located at the

rear of the engine compartment, on the passenger’s side. Flip the handle up and then pull out the dipstick and wipe it with a clean rag or paper towel.

2. Push it back in all the way, wait three seconds and

then pull it back out again.

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How to Add Fluid Refer to the Maintenance Schedule to determine what kind of transmission fluid to use. See “Recommended Fluids and Lubricants” in the Index. Add fluid only after checking the transmission fluid while it is hot. (A cold check is used only as a reference.) If the fluid level is low, add only enough of the proper fluid to bring the level up to the HOT area for a hot check. It doesn’t take much fluid, generally less than one pint (0.5 L). Don’t overfill.

NOTICE:

We recommend you use only fluid labeled DEXRONR-III, because fluid with that label is made especially for your automatic transmission. Damage caused by fluid other than DEXRONR-III is not covered by your new vehicle warranty.

D After adding fluid, recheck the fluid level as

described under “How to Check.”

D When the correct fluid level is obtained, push the dipstick back in all the way; then flip the handle down to lock the dipstick in place.

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Manual Transmission Fluid When to Check A good time to have it checked is when the engine oil is changed. However, the fluid in your manual transmission doesn’t require changing. How to Check Because this operation can be a little difficult, you may choose to have this done at your GM dealership Service Department. If you do it yourself, be sure to follow all the instructions here, or you could get a false reading.

NOTICE:

Too much or too little fluid can damage your transmission. Too much can mean that some of the fluid could come out and fall on hot engine parts or exhaust system parts, starting a fire. Be sure to get an accurate reading if you check your transmission fluid.

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How to Add Fluid Here’s how to add fluid. Refer to the Maintenance Schedule to determine what kind of fluid to use. See “Recommended Fluids and Lubricants” in the Index. 1. Remove the filler plug. 2. Add fluid at the filler plug hole. Add only enough fluid to bring the fluid level up to the bottom of the filler plug hole.

3. Install the filler plug. Be sure the plug is fully seated. Hydraulic Clutch The hydraulic clutch system in your vehicle is self-adjusting. A slight amount of play (1/4 inch to 1/2 inch or 6 mm to 12 mm) in the pedal is normal. It isn’t a good idea to “top off” your clutch fluid. Adding fluid won’t correct a leak. A fluid loss in this system could indicate a problem. Have the system inspected and repaired.

Check the fluid level only when your engine is off, the vehicle is parked on a level place and the transmission is cool enough for you to rest your fingers on the transmission case. Then, follow these steps:

1. Remove the filler plug. 2. Check that the lubricant level is up to the bottom of

the filler plug hole.

3. If the fluid level is good, install the plug and be sure

it is fully seated. If the fluid level is low, add more fluid as described in the next steps.

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When to Check and What to Use

How to Check Lubricant

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Refer to the Maintenance Schedule to determine how often you should check the fluid level in your clutch master cylinder reservoir and for the proper fluid. See “Owner Checks and Services” and “Recommended Fluids and Lubricants” in the Index.

How to Check The proper fluid should be added if the level does not reach the bottom of the diaphragm when it’s in place in the reservoir. See the instructions on the reservoir cap. Rear Axle When to Check and Change Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant and when to change it. See “Scheduled Maintenance Services” in the Index.

If the level is below the bottom of the filler plug hole, you’ll need to add some lubricant. Add enough lubricant to raise the level to the bottom of the filler plug hole. What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See “Recommended Fluids and Lubricants” in the Index.

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C3 (3500 HD) Trucks Equipped with Dana Rear Axle Additional rear axle scheduled maintenance is required on 3500 HD models equipped with Dana rear axles when they are driven under the following conditions: D Extreme loading (at or near GVWR) or trailer

towing, and:

D Operation above 45 mph (70 km/h) for extended

periods of time

Vehicles used in any of these conditions require the rear axle lubricant be changed every 30,000 miles (50 000 km). Fluid capacity is 4.12 quarts (3.9 L). 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. Transfer Case

When to Check Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant. See “Periodic Maintenance Inspections” in the Index.

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How to Check Lubricant

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If the level is below the bottom of the filler plug hole, you’ll need to add some lubricant. Add enough lubricant to raise the level to the bottom of the filler plug hole. Use care not to overtighten the plug.

What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See “Recommended Fluids and Lubricants” in the Index.

Front Axle

When to Check and Change Lubricant Refer to the Maintenance Schedule to determine how often to check the lubricant and when to change it. See “Scheduled Maintenance Services” in the Index.

How to Check Lubricant

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When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole.

What to Use Refer to the Maintenance Schedule to determine what kind of lubricant to use. See “Recommended Fluids and Lubricants” in the Index. Radiator Pressure Cap (Gasoline Engine)

If the level is below the bottom of the filler plug hole, you may need to add some lubricant. When the differential is cold, add enough lubricant to raise the level to 1/2 inch (12 mm) below the filler plug hole.

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The radiator pressure cap must be tightly installed with the arrows on the cap lined up with the overflow tube on the radiator filler neck.

NOTICE:

Your radiator cap is a 15 psi (105 kPa) pressure-type cap and must be tightly installed to prevent coolant loss and possible engine damage from overheating. Be sure the arrows on the cap line up with the overflow tube on the radiator filler neck.

Thermostat Engine coolant temperature is controlled by a thermostat in the engine coolant system. The thermostat stops the flow of coolant through the radiator until the coolant reaches a preset temperature. When you replace your thermostat, an ACR thermostat is recommended.

Engine Coolant The cooling system in your vehicle is filled with DEX-COOLR engine coolant. This coolant is designed to remain in your vehicle for 5 years or 150,000 miles (240 000 km), whichever occurs first, if you add only DEX-COOLR extended life coolant. The following explains your cooling system and how to add coolant when it is low. If you have a problem with engine overheating, see “Engine Overheating” in the Index. A 50/50 mixture of clean, drinkable water and DEX-COOLR coolant will: D Give freezing protection down to -34_F (-37_C). D Give boiling protection up to 265_F (129_C). D Protect against rust and corrosion. D Help keep the proper engine temperature. D Let the warning gages work as they should.

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NOTICE:

CAUTION:

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When adding coolant, it is important that you use only DEX-COOLR (silicate-free) coolant. If coolant other than DEX-COOL is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner -- at 30,000 miles (50 000 km) or 24 months, whichever occurs first. Damage caused by the use of coolant other than DEX-COOLR is not covered by your new vehicle warranty.

What to Use Use a mixture of one-half clean, drinkable water and one-half DEX-COOLR coolant which won’t damage aluminum parts. If you use this coolant mixture, you don’t need to add anything else.

Adding only plain water to your cooling system can be dangerous. Plain water, or some other liquid like alcohol, can boil before the proper coolant mixture will. Your vehicle’s coolant warning system is set for the proper coolant mixture. With plain water or the wrong mixture, your engine could get too hot but you wouldn’t get the overheat warning. Your engine could catch fire and you or others could be burned. Use a 50/50 mixture of clean, drinkable water and DEX-COOLR coolant.

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NOTICE:

If you use an improper coolant mixture, your engine could overheat and be badly damaged. The repair cost wouldn’t be covered by your warranty. Too much water in the mixture can freeze and crack the engine, radiator, heater core and other parts.

If you have to add coolant more than four times a year, have your dealer check your cooling system.

NOTICE:

If you use the proper coolant, you don’t have to add extra inhibitors or additives which claim to improve the system. These can be harmful.

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Checking Coolant

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If your vehicle has a diesel engine, see “Checking Coolant” in the Diesel Engine Supplement. The coolant recovery tank is located on the passenger’s side at the rear corner of the engine compartment. The vehicle must be on a level surface. When your engine is cold, the coolant level should be at the COLD mark, or a little higher. When your engine is warm, the level should be up to the HOT mark, or a little higher.

Adding Coolant If you need more coolant, add the proper DEX-COOLR coolant mixture at the coolant recovery tank.

Add coolant mixture at the recovery tank, but be careful not to spill it.

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CAUTION:

Turning the radiator pressure cap when the engine and radiator are hot can allow steam and scalding liquids to blow out and burn you badly. With the coolant recovery tank, you will almost never have to add coolant at the radiator. Never turn the radiator pressure cap -- even a little -- when the engine and radiator are hot.

CAUTION:

You can be burned if you spill coolant on hot engine parts. Coolant contains ethylene glycol, and it will burn if the engine parts are hot enough. Don’t spill coolant on a hot engine.

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How To Check Power Steering Fluid When the engine compartment is cool, wipe the cap and the top of the reservoir clean, then unscrew the cap and wipe the dipstick with a clean rag. Replace the cap and completely tighten it. Then remove the cap again and look at the fluid level on the dipstick. The level should be at the FULL COLD mark. If necessary, add only enough fluid to bring the level up to the mark. What to Use To determine what kind of fluid to use, see “Recommended Fluids and Lubricants” in the Index. Always use the proper fluid. Failure to use the proper fluid can cause leaks and damage hoses and seals.

Power Steering Fluid

When to Check Power Steering Fluid It is not necessary to regularly check power steering fluid unless you suspect there is a leak in the system or you hear an unusual noise. A fluid loss in this system could indicate a problem. Have the system inspected and repaired.

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Windshield Washer Fluid What to Use When you need windshield washer fluid, be sure to read the manufacturer’s instructions before use. If you will be operating your vehicle in an area where the temperature may fall below freezing, use a fluid that has sufficient protection against freezing. Adding Washer Fluid

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NOTICE:

D When using concentrated washer fluid,

follow the manufacturer’s instructions for adding water.

D Don’t mix water with ready-to-use washer fluid. Water can cause the solution to freeze and damage your washer fluid tank and other parts of the washer system. Also, water doesn’t clean as well as washer fluid.

D Fill your washer fluid tank only

three-quarters full when it’s very cold. This allows for expansion if freezing occurs, which could damage the tank if it is completely full.

D Don’t use engine coolant (antifreeze) in your windshield washer. It can damage your washer system and paint.

Open the cap labeled WASHER FLUID ONLY. Add washer fluid until the tank is full.

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So, it isn’t a good idea to “top off” your brake fluid. Adding brake fluid won’t correct a leak. If you add fluid when your linings are worn, then you’ll have too much fluid when you get new brake linings. You should add (or remove) brake fluid, as necessary, only when work is done on the brake hydraulic system.

CAUTION:

If you have too much brake fluid, it can spill on the engine. The fluid will burn if the engine is hot enough. You or others could be burned, and your vehicle could be damaged. Add brake fluid only when work is done on the brake hydraulic system.

Refer to the Maintenance Schedule to determine when to check your brake fluid. See “Periodic Maintenance Inspections” in the Index.

Brakes Brake Fluid

Your brake master cylinder reservoir is here. It is filled with DOT-3 brake fluid.

There are only two reasons why the brake fluid level in the reservoir might go down. The first is that the brake fluid goes down to an acceptable level during normal brake lining wear. When new linings are put in, the fluid level goes back up. The other reason is that fluid is leaking out of the brake system. If it is, you should have your brake system fixed, since a leak means that sooner or later your brakes won’t work well, or won’t work at all.

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Checking Brake Fluid

You can check the brake fluid without taking off the cap. Just look at the brake fluid reservoir. The fluid level should be above MIN. If it isn’t, have your brake system checked to see if there is a leak. After work is done on the brake hydraulic system, make sure the level is above the MIN but not over the MAX mark.

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What to Add When you do need brake fluid, use only DOT-3 brake fluid. Refer to “Recommended Fluids and Lubricants” in the Index. Use new brake fluid from a sealed container only. Always clean the brake fluid reservoir cap and the area around the cap before removing it. This will help keep dirt from entering the reservoir.

CAUTION:

With the wrong kind of fluid in your brake system, your brakes may not work well, or they may not even work at all. This could cause a crash. Always use the proper brake fluid.

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NOTICE:

D 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.

D 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 “Appearance Care” in the Index.

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Brake Wear If you have a C 3500 HD model, it has four-wheel disc brakes without wear indicators. If you ever hear a brake rubbing noise, have the brake linings inspected. If your pickup is not a C 3500 HD model, it has front disc brakes and rear drum brakes. Disc brake pads (except C 3500 HD models) 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.

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Brake linings should always be replaced as complete axle sets. See “Brake System Inspection” in Section 7 of this manual under Part C “Periodic Maintenance Inspections.” 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 disc brakes adjust for wear. If your brake pedal goes down farther than normal, your rear drum brakes may need adjustment. Adjust them by backing up and firmly applying the brakes a few times.

NOTICE:

Continuing to drive with worn-out brake pads could result in costly brake repair.

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. Properly torqued wheel nuts are necessary to help prevent brake pulsation. When tires are rotated, inspect brake pads for wear and evenly torque wheel nuts in the proper sequence to GM specifications. If you have rear drum brakes, they don’t have wear indicators, but if you ever hear a rear brake rubbing noise, have the rear brake linings inspected immediately. Also, the rear brake drums should be removed and inspected each time the tires are removed for rotation or changing. When you have the front brake pads replaced, have the rear brakes inspected, too.

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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 have to have new ones put in -- be sure you get new approved GM replacement parts. If you don’t, 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’ve come to expect can change in many other ways if someone puts in the wrong replacement brake parts. Battery Your new vehicle comes with an ACDelco FreedomR battery. When it’s time for a new battery, we recommend an ACDelco Freedom battery. Get one that has the replacement number shown on the original battery’s label.

Vehicle Storage If you’re not going to drive your vehicle for 25 days or more, remove the black, negative (-) cable from the battery. This will help keep your battery from running down.

CAUTION:

Batteries have acid that can burn you and gas that can explode. You can be badly hurt if you aren’t careful. See “Jump Starting” in the Index for tips on working around a battery without getting hurt.

Contact your dealer to learn how to prepare your vehicle for longer storage periods. Also, for your audio system, see “Theft-Deterrent Feature” in the Index.

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Bulb Replacement For any bulb changing procedure not listed in this section, contact your GM dealership Service Department. Before you replace any bulbs, be sure that all the lamps are off and the engine isn’t running. See “Replacement Bulbs” in the Index for the proper types of bulbs to use. Halogen Bulbs

CAUTION:

Halogen bulbs have pressurized gas inside and can burst if you drop or scratch the bulb. You or others could be injured. Be sure to read and follow the instructions on the bulb package.

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Headlamps

Sealed Beam Lamps

1. Remove the four

screws from the headlamp retainer.

2. Pull the headlamp out and remove the retainer.

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3. Unplug and remove

the headlamp.

Composite Headlamps

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4. Plug in the new headlamp and put it in place. 5. Install the retainer to the headlamp and tighten

the screws.

1. Remove the two hex head pins at the

locations shown

2. Pull out the headlamp lens assembly. 3. Unplug the electrical connector.

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4. Turn the bulb

counterclockwise and remove it.

Front Turn Signal Lamps (Sealed Beam Headlamps)

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1. Remove the two screws

at the inside edge of the parking/turn signal lamp assembly.

5. Put the new bulb into the assembly and turn it

clockwise until it is tight.

6. Plug in the electrical connector. 7. Put the headlamp lens assembly back into the

vehicle. Install and tighten the two hex head pins.

2. Remove the lamp assembly by swinging it out from the inside edge and sliding it out at the outside edge. 3. Squeeze the tab on the side of the lamp socket while

turning the socket counterclockwise.

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4. Pull the socket out of the

lamp assembly.

Front Turn Signal Lamps (Composite Headlamps)

5. Push in gently on

the bulb, turn it counterclockwise and remove it from the socket.

1. Remove the four screws

and take out the parking/turn signal lamp assembly.

6. Put the new bulb into the socket, gently press in on

the bulb and turn it clockwise until it is tight.

7. Put the socket back into the lamp assembly and turn

it clockwise until it locks.

8. Put the parking/turn signal lamp assembly back into

the vehicle and tighten the screws.

2. Squeeze the tab on the side of the lamp socket while

turning the socket counterclockwise.

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3. Pull the socket out of

the lamp assembly.

Front Sidemarker Lamps (Composite Headlamps)

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1. Remove the four screws

and pull out the parking/turn signal lamp assembly.

4. Push in gently on the bulb, turn it counterclockwise

and remove it from the socket.

5. Put the new bulb into the socket, gently press in on

the bulb and turn it clockwise until it is tight.

6. Put the socket back into the lamp assembly and turn

it clockwise until it locks.

7. Put the parking/turn signal lamp assembly back into

the vehicle and tighten the four screws.

2. Reach through the opening and turn the sidemarker

bulb socket counterclockwise and remove it.

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3. Pull the bulb straight out

of the socket.

Fender Marker Lamps (Dual Rear Wheel Pickup Models)

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1. Remove the screws and take the fender marker assembly out of the fender.

4. Put a new bulb into the socket and push it in until it

is tight.

5. Put the socket back into the sidemarker assembly

and turn it clockwise to tighten it.

6. Replace the parking/turn signal lamp assembly and

tighten the screws.

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2. Turn the bulb socket counterclockwise and remove it from the lens assembly.

Center High-Mounted Stoplamp (CHMSL)

1. Remove the screws and

lift off the lens.

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3. Pull the bulb straight out of the socket. 4. Put a new bulb into the socket and push it in until it

is tight.

5. Put the socket back into the lens assembly and turn it

clockwise to tighten it.

6. Replace the lens and tighten the screws.

2. Pull the old bulb straight out of the socket.

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3. Put a new bulb into the

socket and push it in until it is tight.

4. Replace the lens and tighten the screws.

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Roof Marker Lamps 1. Remove the screws and lift off the lens. 2. Pull the bulb straight out of the socket. 3. Put a new bulb into the socket and push it in

until it is tight.

4. Replace the lens and tighten the screws. Pickup Box Identification Lamps (Dual Rear Wheel Pickup Models) 1. Remove the screws and lamp assembly. 2. Unplug the lamp assembly harness. 3. Use a screwdriver to gently pry the individual lamp

from the lamp housing.

4. Unplug the lamp at the connector. 5. Plug in a new lamp and snap it into the housing. 6. Reinstall the lamp housing.

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Taillamps (Pickup Models) 1. Open the tailgate.

2. Remove the two rear

lamp assembly screws near the tailgate latch and pull out the lamp assembly.

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3. Remove the screws

from the bulb retainer and take it off the lamp assembly.

4. Pull the old bulb straight

out of the socket.

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4. Push in gently on

the bulb, turn it counterclockwise and remove it from the socket.

5. Put in a new bulb and, pushing in gently, turn it

clockwise until it is tight.

6. Put the socket back in the lamp assembly and replace

the lens and lens seal.

5. Put in a new bulb and push it straight in until it

is tight.

6. Replace the bulb retainer. 7. Replace the rear lamp assembly and tighten

the screws.

8. Close the tailgate. Taillamps (Chassis Cab Models) 1. Using your hands, peel the rubber seal away from

the lens.

2. Lift the lens off the

lamp assembly.

3. Slide the socket out of the lamp assembly.

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Windshield Wiper Blade Replacement Windshield wiper blades should be inspected at least twice a year for wear and cracking. See “Wiper Blade Check” in Section 7 of this manual under Part B “Owner Checks and Services” for more information. Replacement blades come in different types and are removed in different ways. For proper type and length, see “Normal Maintenance Replacement Parts” in the Index. Here’s how to remove the Shephard’s Hook type.

To replace the windshield wiper blade assembly: 1. Lift the wiper arm and rotate the blade until it is

facing away from the windshield.

2. Push the release lever and slide the wiper assembly

toward the driver’s side of the vehicle.

3. Install a new blade by reversing Steps 1 and 2.

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Tires Your new vehicle comes with high-quality tires made by a leading tire manufacturer. If you ever have questions about your tire warranty and where to obtain service, see your GM Warranty booklet for details.

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CAUTION:

Poorly maintained and improperly used tires are dangerous. D Overloading your tires can cause

overheating as a result of too much friction. You could have an air-out and a serious accident. See “Loading Your Vehicle” in the Index.

D Underinflated tires pose the same danger as

overloaded tires. The resulting accident could cause serious injury. Check all tires frequently to maintain the recommended pressure. Tire pressure should be checked when your tires are cold.

D Overinflated tires are more likely to be

cut, punctured or broken by a sudden impact -- such as when you hit a pothole. Keep tires at the recommended pressure.

D Worn, old tires can cause accidents. If your

tread is badly worn, or if your tires have been damaged, replace them.

Inflation -- Tire Pressure The Certification/Tire label, which is on the rear edge of the driver’s door, or on the incomplete vehicle document in the cab, shows the correct inflation pressures for your tires when they’re cold. “Cold” means your vehicle has been sitting for at least three hours or driven no more than 1 mile (1.6 km).

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NOTICE:

Don’t let anyone tell you that underinflation or overinflation is all right. It’s not. If your tires don’t have enough air (underinflation), you can get the following: D Too much flexing D Too much heat D Tire overloading D Bad wear D Bad handling D Bad fuel economy. If your tires have too much air (overinflation), you can get the following: D Unusual wear D Bad handling D Rough ride D Needless damage from road hazards.

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When to Check Check your tires once a month or more. Also, check the tire pressure of the spare tire.

How to Check Use a good quality pocket-type gage to check tire pressure. You can’t tell if your tires are properly inflated simply by looking at them. Radial tires may look properly inflated even when they’re underinflated. Be sure to put the valve caps back on the valve stems. They help prevent leaks by keeping out dirt and moisture. Tire Inspection and Rotation Tires should be rotated every 6,000 to 8,000 miles (10 000 to 13 000 km). Any time you notice unusual wear, rotate your tires as soon as possible and check wheel alignment. Also check for damaged tires or wheels. See “When It’s Time for New Tires” and “Wheel Replacement” later in this section for more information. If your vehicle has dual rear wheels, also see “Dual Tire Operation” later in this section.

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The purpose of regular rotation is to achieve more uniform wear for all tires on the vehicle. The first rotation is the most important. See “Scheduled Maintenance Services” in the Index for scheduled rotation intervals.

If your vehicle has single rear wheels, always use one of the correct rotation patterns shown here when rotating your tires. If your vehicle has front tires with different load ranges or tread designs (such as all season vs. on/off road) than the rear tires, don’t rotate your tires front to rear.

If your vehicle has dual rear wheels and the load range and tread design for your front tires is the same as your rear tires, always use one of the correct rotation patterns shown here when rotating your tires.

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If your vehicle has dual rear wheels and the load range or tread design for your front tires is different from your rear tires, always use the correct rotation pattern shown here when rotating your tires.

The dual tires are rotated as a pair, and the inside rear tires become the outside rear tires. When you install dual wheels, be sure the vent holes in the inner and outer wheels on each side are lined up. After the tires have been rotated, adjust the front and rear inflation pressures as shown on the Certification/Tire label. Make certain that all wheel nuts are properly tightened. See “Wheel Nut Torque” in the Index.

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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 an accident. 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. (See “Changing a Flat Tire” in the Index.)

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When It’s Time for New Tires

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One way to tell when it’s time for new tires is to check the treadwear indicators, which will appear when your tires have only 1/16 inch (1.6 mm) or less of tread remaining. Some commercial truck tires may not have treadwear indicators.

You need a new tire if any of the following statements are true: D You can see the indicators at three or more places

around the tire.

D You can see cord or fabric showing through the

tire’s rubber.

D The tread or sidewall is cracked, cut or snagged deep

enough to show cord or fabric.

D The tire has a bump, bulge or split. D The tire has a puncture, cut or other damage that

can’t be repaired well because of the size or location of the damage.

Dual Tire Operation When the vehicle is new, or whenever a wheel, wheel bolt or wheel nut is replaced, check the wheel nut torque after 100, 1,000 and 6,000 miles (160, 1 600 and 10 000 km) of driving. For proper torque, see “Wheel Nut Torque” in the Index. The outer tire on a dual wheel setup generally wears faster than the inner tire. Your tires will wear more evenly and last longer if you rotate the tires periodically. If you’re going to be doing a lot of driving on high-crown roads, you can reduce tire wear by adding 5 psi (35 kPa) to the tire pressure in the outer tires. Be sure to return to the recommended pressures when no longer driving under those conditions. See “Changing a Flat Tire” in the Index for more information.

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CAUTION:

If you operate your vehicle with a tire that is badly underinflated, the tire can overheat. An overheated tire can lose air suddenly or catch fire. You or others could be injured. Be sure all tires (including the spare, if any) are properly inflated.

Buying New Tires To find out what kind and size of tires you need, look at the Certification/Tire label. The tires installed on your vehicle when it was new had a Tire Performance Criteria Specification (TPC Spec) number on each tire’s sidewall. When you get new tires, get ones with that same TPC Spec number. That way your vehicle will continue to have tires that are designed to give proper endurance, handling, speed rating, traction, ride and other things during normal service on your vehicle. If your tires have an all-season tread design, the TPC number will be followed by an “MS” (for mud and snow).

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If you ever replace your tires with those not having a TPC Spec number, make sure they are the same size, load range, speed rating and construction type (bias, bias-belted or radial) as your original tires.

CAUTION:

Mixing tires could cause you to lose control while driving. If you mix tires of different sizes or types (radial and bias-belted tires), the vehicle may not handle properly, and you could have a crash. Using tires of different sizes may also cause damage to your vehicle. Be sure to use the same size and type tires on all wheels.

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CAUTION:

If you use bias-ply tires on your vehicle, the wheel rim flanges could develop cracks after many miles of driving. A tire and/or wheel could fail suddenly, causing a crash. Use only radial-ply tires with the wheels on your vehicle.

Uniform Tire Quality Grading The following information relates to the system developed by the United States National Highway Traffic Safety Administration, which grades tires by treadwear, traction and temperature performance. (This applies only to vehicles sold in the United States.) The grades are molded on the sidewalls of most passenger car tires. The Uniform Tire Quality Grading system does not apply to deep tread, winter-type snow tires, space-saver or temporary use spare tires, tires with nominal rim diameters of 10 to 12 inches (25 to 30 cm), or to some limited-production tires. While the tires available on General Motors passenger cars and light trucks may vary with respect to these grades, they must also conform to Federal safety requirements and additional General Motors Tire Performance Criteria (TPC) standards.

Treadwear The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test course. For example, a tire graded 150 would wear one and a half (1 1/2) times as well on the government course as a tire graded 100. The relative performance of tires depends upon the actual conditions of their use, however, and may depart significantly from the norm due to variations in driving habits, service practices and differences in road characteristics and climate. Traction -- AA, A, B, C The traction grades, from highest to lowest, are AA, A, B, and C. Those grades represent the tire’s ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. A tire marked C may have poor traction performance. Warning: The traction grade assigned to this tire is based on straight-ahead braking traction tests, and does not include acceleration, cornering, hydroplaning, or peak traction characteristics.

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Temperature -- A, B, C The temperature grades are A (the highest), B, and C, representing the tire’s resistance to the generation of heat and its ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained high temperature can cause the material of the tire to degenerate and reduce tire life, and excessive temperature can lead to sudden tire failure. The grade C corresponds to a level of performance which all passenger car tires must meet under the Federal Motor Vehicle Safety Standard No. 109. Grades B and A represent higher levels of performance on the laboratory test wheel than the minimum required by law. Warning: The temperature grade for this tire is established for a tire that is properly inflated and not overloaded. Excessive speed, underinflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.

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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:

Using the wrong replacement wheels, wheel bolts or wheel nuts on your vehicle can be dangerous. It could affect the braking and handling of your vehicle, make your tires lose air and make you lose control. You could have a collision in which you or others could be injured. Always use the correct wheel, wheel bolts and wheel nuts for replacement.

Wheel Alignment and Tire Balance The wheels on your vehicle were aligned and balanced carefully at the factory to give you the longest tire life and best overall performance. Scheduled wheel alignment and wheel balancing are not needed. However, if you notice unusual tire wear or your vehicle 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