GM Service Manual Online
For 1990-2009 cars only

If your vehicle has four-wheel drive, the engine's driving power can be sent 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. You should use Two-Wheel High for most normal driving conditions.

Notice: Driving on clean, dry pavement in Four-Wheel-Drive High or Four-Wheel-Drive Low for an extended period of time may cause premature wear on your vehicle's powertrain. Do not drive on clean, dry pavement in Four-Wheel-Drive High or Four-Wheel-Drive Low for extended periods of time.

Automatic Transfer Case

Your vehicle will have one of the following transfer case knobs.


Object Number: 810272  Size: A2

Object Number: 1645805  Size: A2

If your vehicle has four-wheel drive, the transfer case knob is located to the right of the steering wheel on the instrument panel. Use this knob to shift into and out of four-wheel drive.

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

A4WD, AUTO (Automatic Four-Wheel Drive):  This setting is ideal for use when road conditions are variable. When driving your vehicle in automatic four-wheel drive, the front axle is engaged, but the vehicle's power is sent 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.

4HI, 4 (Four-Wheel High): This setting should be used 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.

4LO, 4 (Four-Wheel Low): This setting also engages your front axle and delivers extra torque. It sends maximum power to all four wheels. You might choose this setting if you are driving off-road in deep sand, deep mud, and climbing or descending steep hills.

Caution: Shifting the transfer case to 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 Neutral. See Parking Brake.

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

An indicator light in the knob will show you which position the transfer case is 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 stay on 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 Four-Wheel Drive Warning Light on the instrument panel cluster stays on, you should take your vehicle to your dealer for service. See Service Four-Wheel Drive Warning Light for further information.

Shifting Into Four-Wheel High or Automatic Four-Wheel Drive

Turn the knob to Four-Wheel High or Automatic Four-Wheel Drive. This can be done at any speed unless you are shifting out of Four-Wheel Low. The indicator light will flash while shifting. It will remain on when the shift is complete.

Shifting Into Two-Wheel High

Turn the knob to Two-Wheel High. This can be done at any speed unless you are shifting out of Four-Wheel Low.

Shifting Into Four-Wheel Low

To shift to Four-Wheel Low, the vehicle's engine must be running and the vehicle must be stopped or moving less than 2 mph (3.2 km/h) with the transmission in NEUTRAL (N). The preferred method for shifting into Four-Wheel Low is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob to Four-Wheel Low. You must wait for the Four-Wheel Low indicator light to stop flashing and stay on before shifting the transmission into gear.

If you turn the knob to Four-Wheel Low 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 2 mph (3.2 km/h) and the transmission is in NEUTRAL (N). After 30 seconds, the transfer case will return to the setting last chosen.

Shifting Out of Four-Wheel Low

To shift from Four-Wheel Low to Four-Wheel High, Auto Four-Wheel Drive, or Two-Wheel High, your vehicle must be stopped or moving less than 2 mph (3.2 km/h) with the transmission in NEUTRAL (N) and the engine running. The preferred method for shifting out of Four-Wheel Low is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob to Four-Wheel High, Auto Four-Wheel Drive, or Two-Wheel High. You must wait for the Four-Wheel High, Auto Four-Wheel Drive, or Two-Wheel High indicator light to stop flashing and stay off before shifting your transmission into gear.

If the knob is turned to Four Wheel-High, Auto Four-Wheel Drive, or Two-Wheel High when your vehicle is in gear and/or moving, the Four-Wheel High, Auto Four-Wheel Drive, or Two-Wheel High indicator light will flash for 30 seconds. It will not complete the shift unless your vehicle is moving less than 2 mph (3.2 km/h) with the transmission in NEUTRAL (N).

Shifting into NEUTRAL

Before shifting the transfer case to NEUTRAL, first make sure the vehicle is parked so that it will not roll.

  1. Set the parking brake.
  2. Start the vehicle.
  3. Put the transmission in NEUTRAL (N).
  4. Shift the transfer case to Two-Wheel High.
  5. Turn the transfer case knob all of the way past Four-Wheel Low and hold it there for a minimum of 10 seconds. The neutral indicator light will come on.
  6. With the engine running, shift the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second, to ensure that the transfer case is in NEUTRAL.
  7. Turn the engine off, by turning the key to ACCESSORY.
  8. Place the transmission shift lever in PARK (P).
  9. Turn the ignition to LOCK.

Shifting Out of NEUTRAL

To shift the transfer case out of NEUTRAL, do the following:

  1. Set the parking brake and apply the regular brake pedal.
  2. Turn the ignition to RUN with the engine off.
  3. Put the transmission in NEUTRAL (N).
  4. Turn the transfer case knob to the desired position (Two-Wheel High, Four-Wheel High, or Auto Four-Wheel Drive).
  5. After the transfer case has shifted out of NEUTRAL, the indicator light will go out.
  6. Release the parking brake.
  7. Start the engine and shift the transmission to the desired position.