GM Service Manual Online
For 1990-2009 cars only

If your vehicle has four-wheel drive, 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. You should use two-wheel drive high (2HI) for most normal driving conditions.

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.

Automatic Transfer Case


Object Number: 810272  Size: A2

If your vehicle is equipped with 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 (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 (Automatic Four-Wheel Drive):  This setting is ideal for use when road conditions are variable. When driving your vehicle in A4WD, 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 2HI.

4HI (Four-Wheel High):  Use 4HI 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 (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 4LO 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 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 four-wheel drive 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 4HI or A4WD

Turn the knob to 4HI or A4WD. This can be done at any speed unless you are shifting out of 4LO. The indicator light will flash while shifting. It will remain illuminated when the shift is complete.

Shifting Into 2HI

Turn the knob to 2HI. This can be done at any speed unless you are shifting out of 4LO.

Shifting Into 4LO

To shift to 4LO, 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 4LO is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob to 4LO. You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission into gear.

If you turn the knob to 4LO when your vehicle is in gear and/or moving, the 4LO 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 4LO

To shift from 4LO to 4HI, A4WD or 2HI 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 4LO is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob to 4HI, A4WD or 2HI. You must wait for the 4HI, A4WD or 2HI indicator light to stop flashing and remain illuminated before shifting your transmission into gear.

If the knob is turned to 4HI, A4WD or 2HI when your vehicle is in gear and/or moving, the 4HI, A4WD or 2HI 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. Turn the transfer case knob all of the way past 4LO and hold it there for a minimum of 10 seconds. The neutral indicator light will come on.
  5. Shift the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second.
  6. Place the transmission shift lever in PARK (P).
  7. Turn the ignition to LOCK.
  8. For information on towing your vehicle see Recreational Vehicle Towing.

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. Start the vehicle with the transmission in PARK (P).
  3. Turn the transfer case knob to the desired shift position (2HI, 4HI or A4WD).
  4. Put the transmission in NEUTRAL (N).
  5. Release the parking brake.
  6. After the transfer case has shifted out of NEUTRAL, the indicator light will go out. Shift the transmission lever to the desired position.

A re-engagement sound is normal when shifting out of NEUTRAL.