GM Service Manual Online
For 1990-2009 cars only

If the vehicle has four-wheel drive, you can send the engine's driving power to all four wheels for extra traction. Read the following before using four-wheel drive.

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.

While driving on clean dry pavement and during tight turns, you may experience a vibration in the steering system.

The vehicle has StabiliTrak®. Shifting into Four-Wheel-Drive Low will turn Traction Control and StabiliTrak® off. See StabiliTrak® System in the index of the Owner Manual for more information.

Front Axle

The front axle engages and disengages automatically when you shift the transfer case. Some delay for the axle to engage or disengage is normal.

Automatic Transfer Case


Object Number: 1657601  Size: A2

The transfer case knob is located to the left of the instrument panel cluster.

Use this dial to shift into and out of four-wheel drive.

You can choose among five driving settings:

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

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

AUTO (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving your vehicle in AUTO, the front axle is engaged, but the vehicle's power is primarily sent to the rear wheels. When the vehicle's software determines a need for more traction, the system will transfer more power to the front wheels. Driving in this mode results in slightly lower fuel economy than Two-Wheel Drive High.

4 (Four-Wheel Drive 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 the front axle to help drive the vehicle. This is the best setting to use when plowing snow.

4 (Four-Wheel Drive Low): This setting also engages the 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 Drive Low if you are driving off-road in deep sand, deep mud, deep snow, and while climbing or descending steep hills. The vehicle has StabiliTrak®. Shifting into Four-Wheel-Drive Low will turn Traction Control and StabiliTrak® off. See StabiliTrak® System in the index of the Owner Manual 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 in the index of the Owner Manual for more information.

N (Neutral): Shift the vehicle's transfer case to N (Neutral) only when towing the vehicle. See Recreational Vehicle Towing or Towing Your Vehicle in the index of the Owner Manual.

If the SERVICE 4 WHEEL DRIVE message stays on, you should take the vehicle to your dealer/retailer for service. See DIC Warnings and Messages for more information.

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

Turn the knob to the Four-Wheel High or AUTO position. This can be done at any speed, except when shifting from Four-Wheel Drive Low. The indicator light will flash while shifting. It will remain on when the shift is completed.

Shifting Into Two-Wheel Drive High

Turn the knob to the Two-Wheel High position. This can be done at any speed, except when shifting from Four-Wheel Drive Low.

See "Shifting Out of Four-Wheel Drive Low" later in this section for more information.

Shifting Into Four-Wheel Drive Low

When Four-Wheel Low is engaged, vehicle speed should be kept below 45 mph (72 km/h). Extended high-speed operation in 4L may damage or shorten the life of the drivetrain.

To shift to the Four-Wheel Drive Low position, the ignition must be in ON/RUN and the vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in N (Neutral). The preferred method for shifting into Four-Wheel Drive Low is to have the vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Turn the knob to the Four-Wheel Drive Low position. You must wait for the Four-Wheel Drive Low indicator light to stop flashing and remain on before shifting the 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.

The vehicle may have significant engagement noise and bump when shifting between Four-Wheel Drive Low and Four-Wheel Drive High ranges or from N (Neutral) while the engine is running.

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

Shifting Out of Four-Wheel Drive Low

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

The vehicle may have significant engagement noise and bump when shifting between Four-Wheel Drive Low and Four-Wheel Drive High ranges or from N (Neutral) while the engine is running.

If the knob is turned to the Four-Wheel Drive High, AUTO, or Two-Wheel Drive High switch position when the vehicle is in gear and/or moving, the Four-Wheel Drive High, AUTO or Two-Wheel Drive High indicator light will flash for 30 seconds but will not complete the shift unless the vehicle is moving less than 3 mph (5 km/h) and the transmission is in N (Neutral).

Shifting into Neutral

To shift the transfer case into N (Neutral):

  1. Make sure the vehicle is parked so that it will not roll.
  2. Set the parking brake and apply the regular brake pedal. See Parking Brake in the index of the Owner Manual for more information.
  3. Start the vehicle or turn the ignition to ON/RUN.
  4. Put the transmission in N (Neutral).
  5. Shift the transfer case to Two-Wheel Drive High.
  6. Turn the transfer case dial clockwise to N (Neutral) until it stops and hold it there until the N (Neutral) light starts blinking. This will take at least 10 seconds. Then slowly release the dial to the Four-Wheel Drive Low position. The N (Neutral) light will come on when the transfer case shift to N (Neutral) is complete.
  7. If the engine is running, verify that the transfer case is in N (Neutral) by shifting the transmission to R (Reverse) for one second, then shift the transmission to D (Drive) for one second.
  8. Turn the ignition to ACC/ACCESSORY, which will turn the engine off.
  9. Place the transmission shift lever in P (Park).
  10. Release the parking brake prior to moving the vehicle.
  11. Turn the ignition to LOCK/OFF.

Shifting Out of Neutral

To shift the transfer case out of N (Neutral):

  1. Set the parking brake and apply the regular brake pedal.
  2. Turn the ignition to ON/RUN with the engine off, and shift the transmission to N (Neutral).
  3. Turn the transfer case dial to the desired transfer case shift position (Two-Wheel Drive High, Four-Wheel Drive High, AUTO).
  4. After the transfer case has shifted out of N (Neutral), the N (Neutral) light will go out.

  5. Release the parking brake prior to moving the vehicle.
  6. 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.

  7. 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.