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 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.

Electronic Transfer Case


Object Number: 809370  Size: A2

If your four-wheel-drive vehicle has the electronic transfer case, the transfer case buttons are to the right of the steering wheel on the instrument panel.

Use these buttons to shift into and out of four-wheel drive. You can choose among three driving settings:

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. When this lamp is lit, it is about one-half as bright as the others.

4HI (Four-Wheel High): This setting engages your front axle to help drive your vehicle. Use 4HI when you need extra traction, such as on snowy or icy roads, or in most off-road situations.

4LO (Four-Wheel Low):  This setting also engages your front axle to give you extra traction. You may never need 4LO. It sends the maximum power to all four wheels. You might choose 4LO if you were driving off-road in sand, mud or deep snow and climbing or descending steep hills. Indicator lights in the buttons show you 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 in for service. An indicator light will flash while shifting. It will remain illuminated when the shift is completed.

Shifting from 2HI to 4HI

Press and release the 4HI button. This can be done at any speed, and the front axle will lock automatically.

Shifting from 4HI to 2HI

Press and release the 2HI button. This can be done at any speed, and the front axle will unlock automatically.

Shifting from 2HI or 4HI to 4LO

To shift from 2HI or 4HI to 4LO, the vehicle must be stopped or moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N) in vehicles equipped with an automatic transmission or the clutch pedal engaged in vehicles equipped with a manual transmission. The preferred method for shifting into 4LO is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the 4LO button. You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission into gear or releasing the clutch pedal.

If the 4LO button is pressed 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 slower than 3 mph (4.8 km/h) and the transmission is in NEUTRAL (N) or the clutch pedal engaged.

On automatic transmission equipped vehicles, if your transfer case does not shift into 4LO, your transmission indicator switch may require adjustment. With your transmission in NEUTRAL (N), press and release the 4LO button. While the 4LO indicator light is flashing, shift your transmission into PARK (P). Wait until the 4LO indicator light remains illuminated before shifting your transmission into gear. This will get you into 4LO, but you should take your vehicle in for service to restore normal operation.

Shifting from 4LO to 4HI or 2HI

To shift from 4LO to 4HI or 2HI, your vehicle must be stopped or moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N) or the clutch pedal engaged. The preferred method for shifting out of 4LO is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the 4HI button. You must wait for the 4HI indicator light to stop flashing and remain illuminated before shifting your transmission into gear or releasing the clutch pedal.

If the 4HI button is pressed when your vehicle is in gear and/or moving, the 4HI indicator light will flash for 30 seconds but not complete the shift unless the vehicle is moving slower than 3 mph (4.8 km/h) and the transmission is in NEUTRAL (N) or the clutch pedal engaged.

On automatic transmission equipped vehicles, if your transfer case does not shift into 4HI, your transmission indicator switch may require adjustment. With your transmission in NEUTRAL (N), press and release the 4HI button. While the 4HI indicator light is flashing, shift your transmission into PARK (P). Wait until the 4HI indicator light remains illuminated before shifting your transmission into gear. This will get you into 4HI, but you should take your vehicle in for service to restore normal operation.

Automatic Transfer Case


Object Number: 807592  Size: A2

If your vehicle is equipped with the automatic transfer case, the transfer case buttons are located to the right of the steering wheel on the instrument panel.

Use these buttons to shift into and out of four-wheel drive. You can choose among four driving settings:

2HI (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.

AUTO 4WD (Automatic Four-Wheel Drive): This setting is ideal for use when road conditions are variable. While 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 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. You may never need 4LO. It sends maximum power to all four wheels. You might choose 4LO if you are driving off-road in deep sand, deep mud, deep snow 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 or Towing Your Vehicle for more information. Indicator lights in the buttons 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 light stays on, you should take your vehicle to your dealer for service. See Service Four-Wheel Drive Warning Light for further information.

Shifting to 4HI or AUTO 4WD

Press and release the 4HI or AUTO 4WD button. This can be done at any speed, and the indicator light will flash while shifting. It will remain illuminated when the shift is complete.

Shifting to 2HI

Press and release the 2HI button. This can be done at any speed.

Shifting to 4LO

To shift to 4LO, the vehicle's engine must be running and the vehicle must be stopped or moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N) or with the clutch pedal pressed for vehicles with manual transmission. The preferred method for shifting into 4LO is to have your vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Press and release the 4LO button. You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission into gear.

If the 4LO button is pressed 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 3 mph (4.8 km/h) and the transmission is in NEUTRAL (N) or with the clutch pedal pressed for vehicles with manual transmission. After 30 seconds, the transfer case will return to the setting last chosen.

Shifting out of 4LO

To shift from 4LO to 4HI, AUTO 4WD or 2HI, your vehicle must be stopped or moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N), or with the clutch pedal pressed for vehicles with manual transmission, 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). Press and release the 4HI, AUTO 4WD or 2HI button. You must wait for the 4HI, AUTO 4WD or 2HI indicator light to stop flashing and remain illuminated before shifting your transmission into gear.

If the 4HI, AUTO 4WD or 2HI button is pressed when your vehicle is in gear and/or moving, the 4HI, AUTO 4WD or 2HI indicator light will flash for 30 seconds but will not complete the shift unless your vehicle is moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N) or with the clutch pedal pressed for vehicles with manual transmission.

Shifting to NEUTRAL

To shift 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. Connect the vehicle to the towing vehicle.
  4. Put the transmission in NEUTRAL (N) or have the clutch pedal pressed for vehicles with manual transmission.
  5. Shift the transfer case to 2HI.
  6. Simultaneously press and hold the 2HI and 4LO buttons for 10 seconds. The NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete.
  7. Shift the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second or FIRST (1) for vehicles with manual transmission.
  8. Turn the ignition to OFF.
  9. Place the transmission shift lever in PARK (P) or FIRST (1) for vehicles with manual transmission.
  10. Release the parking brake prior to towing.

Shifting out of NEUTRAL

To shift out of NEUTRAL:

  1. Set the parking brake and apply the regular brake pedal.
  2. Start the vehicle with the transmission in PARK (P) or FIRST (1) for vehicles with manual transmission.
  3. Press the button for the desired transfer case position (2HI, 4HI, AUTO 4WD or 4LO).
  4. Put the transmission in NEUTRAL (N) or press the clutch pedal for vehicles with manual transmission.
  5. Shift the transmission lever to the desired position. After the transfer case has shifted out of NEUTRAL, the NEUTRAL light will go out.

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