GM Service Manual Online
For 1990-2009 cars only

Full-Time Four-Wheel Drive sends your engine's driving power to all four wheels for extra traction. To get the most out of Full-Time Four-Wheel Drive, you must be familiar with its operation.

Transfer Case Buttons


Object Number: 1555207  Size: B1

The transfer case buttons are located to the right of the instrument panel cluster. Use these switches to shift into and out of the different Full-Time Four-Wheel Drive modes.

You can choose between four modes:

4 (Four-Wheel High): This setting is used for driving in most street and highway situations. You can also use this setting for light or variable off-road conditions.

N (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.

Notice: Driving on pavement in Four-Wheel High Lock or Four Wheel Low Lock for extended periods may cause premature wear on the vehicle powertrain and tires. Do not drive in Four-Wheel High Lock or Four-Wheel Low Lock on pavement for extended periods.

4 (Four-Wheel-High Lock): Use this mode when you need extra traction in most off-road situations such as sand, mud, snow or level, rocky trails.

Notice: Operating the vehicle in Four-Wheel-Low Lock above 30 mph (48 km/h) for any extended period of time could cause damage to the transfer case. Do not operate the vehicle in Four-Wheel-Low Lock above 30 mph (48 km/h) for extended periods.

4 (Four-Wheel-Low Lock): This mode delivers extra torque to all four wheels and is used for extreme off-road conditions. You might choose 4-Wheel-Low Lock if you are driving in off-road situations, such as, deep sand, mud, or snow and climbing or descending steep hills. When in this mode you can also choose to lock the rear axle, if equipped, for additional traction in extreme off-road situations. See Locking Rear Axle .

Indicator lights in the buttons show which mode you are in. The indicator lights will come on briefly when you turn on the ignition the mode the vehicle is in 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 lit 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 SERV 4WD message stays on, you should take your vehicle to your dealer for service. See Service 4WD message under DIC Warnings and Messages .

Shifting between Four-Wheel High and Four-Wheel-High Lock

With the vehicle traveling less than 45 mph (73 km/h), press and release the Four-Wheel High or Four-Wheel-High Lock button. The indicator light will flash while shifting. It will remain lit when the shift is complete.

It may be necessary to drive backwards while turning for a distance of 25 feet (7.5 m) to get the lock feature to disengage.

Shifting into Four-Wheel Low Lock

Notice: Shifting the transmission into gear before the indicator light stops flashing could cause damage to the transfer case. Always wait until the indicator light stops flashing before putting the transmission back in gear.

To shift into Four-Wheel-Low Lock, the ignition must be in ON 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 Lock button. If your vehicle has a manual transmission, the clutch pedal must be pressed to the floor while you press the Four-Wheel-Low Lock button, or the shift will not be completed. You must wait for the Four-Wheel-Low Lock indicator light to stop flashing and remain lit before shifting your transmission in gear.

It is normal for your vehicle to have 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 Lock button is pressed when your vehicle is in gear and/or moving too fast, the Four-Wheel-Low Lock indicator light will flash for 15 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 15 seconds the transfer case will return to the last chosen setting.

Shifting Out of Four-Wheel-Low Lock

Notice: Shifting the transmission into gear before the indicator light stops flashing could cause damage to the transfer case. Always wait until the indicator light stops flashing before putting the transmission back in gear.

To shift out of Four-Wheel-Low Lock, your vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) and the ignition in ON. The preferred method for shifting out of Four-Wheel-Low Lock is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the Four-Wheel High or Four-Wheel-High Lock button. If your vehicle has a manual transmission, the clutch pedal must be pressed to the floor while you press the Four-Wheel High or Four-Wheel-High Lock button, or the shift will not be completed. You must wait for the Four-Wheel High or Four-Wheel-High Lock indicator light to stop flashing and remain lit before shifting your transmission into gear.

It is normal for your vehicle to have 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 or Four-Wheel-High Lock button is pressed when your vehicle is in gear and/or moving too fast, the Four-Wheel High or Four-Wheel-High Lock indicator light will flash for 15 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. Set the parking brake.
  2. Start the vehicle by turning the ignition to START.
  3. Put the transmission in NEUTRAL (N). If your vehicle has a manual transmission, press and hold the clutch pedal down while you perform Steps 5 through 9.
  4. Shift the transfer case to Four-Wheel High.
  5. Caution: Shifting an all-wheel-drive vehicle's transfer case into Neutral can cause the vehicle to roll even if the automatic transmission is in P (Park) or the manual transmission is in any gear. You or others could be injured. Make sure the parking brake is firmly set before you shift the transfer case to Neutral.

  6. Simultaneously press and hold the Four-Wheel High and Four-Wheel-Low Lock buttons for 10 seconds. The NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete.
  7. Press and hold the regular brake pedal and Shift the transmission to REVERSE (R) for one second, then shift the transmission for one second to DRIVE (D) for an automatic transmission, or FIRST (1) for vehicles equipped with a manual transmission and then let out the clutch. This is to ensure the transfer case is in NEUTRAL. If not, repeat this procedure starting at Step 3.
  8. Turn the engine off, by turning the key to ACC.
  9. Place the transmission shift lever in PARK (P) for an automatic transmission, or FIRST (1) for vehicles equipped with a manual transmission.
  10. Turn the ignition to LOCK.

Shifting Out of NEUTRAL

To shift out of NEUTRAL:

  1. Set the parking brake and apply the regular brake pedal.
  2. Shift the transmission to NEUTRAL (N) for an automatic transmission, or press the clutch pedal for vehicles equipped with a manual transmission. Then turn the ignition to ON with the engine off.
  3. Press the button for the desired transfer case shift position (Four-Wheel High, Four-Wheel-High Lock or Four-Wheel-Low Lock).
  4. After the transfer case has shifted out of NEUTRAL the light will go out.

  5. Release the parking brake.
  6. Notice: Shifting the transmission into gear before the indicator light stops flashing could cause damage to the transfer case. Always wait until the indicator light stops flashing before putting the transmission back in gear.

  7. You may start the engine and shift the transmission to the desired position.