GM Service Manual Online
For 1990-2009 cars only

If your vehicle has four-wheel drive, you will see the buttons shown below. You can send your engine's driving power to all four wheels for extra traction. To get the most satisfaction out of four-wheel drive, you must be familiar with its operation. Read the part that follows before using four-wheel drive.

Notice: Driving on clean, dry pavement in four-wheel drive for an extended period of time can cause premature wear on the vehicle's powertrain. Do not drive on clean, dry pavement in Four-Wheel Drive for extended periods of time.

Front Axle Locking Feature

The front axle locks and unlocks automatically when you shift the transfer case. Some delay for the axle to lock or unlock is normal.

For four-wheel drive vehicles with StabiliTrakĀ®, see StabiliTrakĀ® System .

Automatic Transfer Case


Object Number: 870540  Size: A3

The transfer case buttons are located to the left of the instrument panel cluster.

Use these buttons to shift into and out of four-wheel drive.

You can choose among four driving settings:

AUTO 4WD (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving your vehicle in AUTO 4WD, the front axle is engaged, but the vehicle's power is sent only to the rear wheels. When the vehicle senses a loss of traction, the system will automatically engage four-wheel drive. Driving in this mode results in slightly lower fuel economy than Two-Wheel High.

2 (Two Wheel-High): This setting is used for driving in most street and highway situations. Your front axle is not engaged in two-wheel drive. This setting also provides the best fuel economy.

4 (Four Wheel-High): Use the four-wheel high position when you need extra traction, such as on snowy or icy roads or in most off-road situations. This setting also engages your front axle to help drive your vehicle. This is the best setting to use when plowing snow.

4 (Four Wheel-Low): This setting also engages your front axle and delivers extra torque. You may never need this setting. It sends maximum power to all four wheels. You might choose Four Wheel-Low if you are driving off-road in deep sand, deep mud, deep snow, and while climbing or descending steep hills. StabiliTrakĀ® will not engage in this mode. See StabiliTrakĀ® System for more information.

Caution: Shifting the transfer case to N (Neutral) can cause the vehicle to roll even if the transmission is in P (Park). You or someone else could be seriously injured. Be sure to set the parking brake before placing the transfer case in N (Neutral). See Parking Brake .

NEUTRAL (N): Shift the vehicle's transfer case to NEUTRAL only when towing your vehicle. See Recreational Vehicle Towing or Towing Your Vehicle for more information.

Indicator lights in the button show which setting you are in. The indicator lights will come on briefly when you turn on the ignition and one will stay on. If the lights do not come on, you should take your vehicle to your dealer for service. An indicator light will flash while shifting the transfer case. It will remain illuminated when the shift is complete. If for some reason the transfer case cannot make a requested shift, it will return to the last chosen setting.

If the SERVICE 4WD message stays on, you should take your vehicle to your dealer for service. See "Service 4WD message" under Driver Information Center (DIC) .

Shifting Into Four-Wheel High or AUTO 4WD (Automatic Four Wheel Drive)

Press and release the Four-Wheel High or AUTO 4WD button. This can be done at any speed, except when shifting from Four Wheel-Low, and the indicator light will flash while shifting. It will remain on when the shift is completed.

Shifting Into Two-Wheel High

Press and release the Two-Wheel High button. This can be done at any speed, except when shifting from Four-Wheel Low.

Shifting Into Four-Wheel Low

To shift to the Four-Wheel Low position, the ignition must be in RUN and the vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N). The preferred method for shifting into four-wheel low is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the Four-Wheel Low button. You must wait for the four-wheel low indicator light to stop flashing and remain on before shifting your transmission in gear.

Notice: Shifting the transmission into gear before the Four-Wheel Drive Low indicator light has stopped flashing could damage the transfer case. To help avoid damaging the vehicle, always wait for the Four-Wheel Drive Low indicator light to stop flashing before shifting the transmission into gear.

It is typical for your vehicle to exhibit significant engagement noise and bump when shifting between Four-Wheel Low and Four-Wheel High ranges or from NEUTRAL with the engine running.

If the Four-Wheel Low button is pressed when your vehicle is in gear and/or moving, the Four-Wheel Low indicator light will flash for 30 seconds and not complete the shift unless your vehicle is moving less than 3 mph (5 km/h) and the transmission is in NEUTRAL (N). After 30 seconds the transfer case will shift to Four-Wheel High mode.

Shifting Out of Four-Wheel Low

To shift from Four-Wheel Low to Four-Wheel High, AUTO 4WD or Two-Wheel High, your vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) and the ignition in RUN. The preferred method for shifting out of Four-Wheel Low is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the Four-Wheel High, AUTO 4WD or Two-Wheel High button. You must wait for the Four-Wheel High, AUTO 4WD or Two-Wheel High indicator light to stop flashing and remain on before shifting your transmission into gear.

Notice: Shifting the transmission into gear before the Four-Wheel Drive Low indicator light has stopped flashing could damage the transfer case. To help avoid damaging the vehicle, always wait for the Four-Wheel Drive Low indicator light to stop flashing before shifting the transmission into gear.

It is typical for your vehicle to exhibit significant engagement noise and bump when shifting between Four-Wheel Low and Four-Wheel High ranges or from NEUTRAL with the engine running.

If the Four-Wheel High, AUTO 4WD or Two Wheel High switch is pressed when your vehicle is in gear and/or moving, the Four-Wheel High, AUTO 4WD or Two-Wheel High indicator light will flash for 30 seconds but will not complete the shift unless your vehicle is moving less than 3 mph (5 km/h) and the transmission is in NEUTRAL (N).

Shifting into NEUTRAL

To shift the transfer case to NEUTRAL do the following:

  1. Make sure the vehicle is parked so that it will not roll.
  2. Set the parking brake.
  3. Start the vehicle or turn the ignition to RUN.
  4. Put the transmission in NEUTRAL (N).
  5. Shift the transfer case to Two-Wheel High.
  6. Simultaneously press and hold the Two-Wheel High and Four-Wheel Low buttons for 10 seconds. The NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete.
  7. If the engine is running, verify that the transmission is in NEUTRAL (N) by shifting the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second.
  8. Turn the ignition to ACCESSORY, which will turn the engine off.
  9. Place the transmission shift lever in PARK (P).
  10. Turn the ignition to LOCK.

Shifting Out of NEUTRAL

To shift out of NEUTRAL do the following:

  1. Set the parking brake and apply the regular brake pedal.
  2. Shift the transmission to NEUTRAL (N) and turn the ignition to RUN with the engine off.
  3. Press the button for the desired transfer case shift position (Two-Wheel High, Four-Wheel High, AUTO 4WD, or Four-Wheel Low).
  4. After the transfer case has shifted out of NEUTRAL the NEUTRAL light will go out.
  5. Release the parking brake.
  6. Start the engine and shift the transmission to the desired position.

Excessively shifting the transfer case into or out of the different modes may cause the transfer case to enter the shift protection mode. This will protect the transfer case from possible damage and will only allow the transfer case to respond to one shift per 10 seconds. The transfer case may stay in this mode for up to three minutes.