Four-Wheel Drive. GMC Truck GMC C Sierra

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC C Sierra - 2WD 🢒 Features and Controls 🢒 Starting and Operating Your Vehicle 🢒 Four-Wheel Drive

Table 1:	Recommended Transfer Case Settings
Table 2:	Recommended Transfer Case Settings
Table 3:	Recommended Transfer Case Settings

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. See the appropriate text for the transfer case in your vehicle.

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

Front Axle Locking Feature

The front axle locks and unlocks automatically when you shift the transfer case. Some delay for the axle to lock or unlock is normal.

Manual Transfer Case

The transfer case shift lever is located on the floor to the right of the driver. Use this lever to shift into and out of four-wheel drive.

A 4WD indicator light comes on when you shift into four-wheel drive and the front axle engages. See Four-Wheel-Drive Light .

Some delay between shifting and when the indicator light comes on is normal.

Recommended Transfer Case Settings

Driving Conditions	Transfer Case Settings
Driving Conditions	2H	4H	4L	N
Normal	YES
Severe		YES
Extreme			YES
Vehicle in Tow*				YES
*See Recreational Vehicle Towing or Towing Your Vehicle for further information.

An indicator light near the lever shows you the transfer case settings:

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.

4L (Four-Wheel Low): This setting also engages the front axle and delivers extra torque. You may never need 4L. It sends maximum power to all four wheels. You might choose 4L if you are driving off-road in deep sand, deep mud, deep snow, and while climbing or descending steep hills. When operating in 4L, the gear ratio provides additional torque when compared to 4H. The transmission gear shift feel will be exaggerated.

Caution: Shifting the transfer case to Neutral can cause the vehicle to roll even if the transmission is in P (Park), or if you have a manual transmission, even if you are in gear. 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.

N (Neutral): Shift to this setting only when your vehicle needs to be towed. See Recreational Vehicle Towing or Towing Your Vehicle .

2H (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.

4H (Four-Wheel Drive High): Use this setting 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 your vehicle. This is the best setting to use when plowing snow. You can shift from 2H to 4H or 4H to 2H while the vehicle is moving. The front axle will engage faster if you take your foot off of the accelerator for a couple of seconds after you shift. In extremely cold weather, it may be necessary to stop or slow the vehicle to shift into 4H.

When Using the Manual Transfer Case

•	Shifting should be made using quick motions. Shifting slowly may make it more difficult to shift.

•	You may notice that it is harder to shift when the vehicle is cold. After the vehicle warms up the shifting will return to normal.

•	While in 4H or 4L you may experience reduced fuel economy.

•	Avoid driving in four-wheel drive on clean, dry pavement. Doing this may cause the tires to wear faster, and make your transfer case harder to shift, and run noisier.

Shifting from 2H (Two-Wheel Drive High) to 4H (Four-Wheel Drive High)

•	Shifts between 2H and 4H can be made at any vehicle speed.

•	It is easiest to shift the transfer case when maintaining a constant speed or during a slight acceleration. If possible, avoid shifting while slowing down, as it will make it harder to shift.

•	Shift the transfer case lever in one continuous motion into either the 4H or 2H position.

•	In extremely cold weather, it may be necessary to slow or stop the vehicle to shift into 4H until your vehicle has warmed up.

•	While in 4H, your vehicle can be driven at any posted legal speed limit.

Shifting In or Out of 4L (Four-Wheel Drive Low)

Notice: Shifting the transfer case into 4L while moving at speeds faster than 3 mph (5 km/h) may cause premature wear to the transfer case, and may cause the gears to grind. To avoid causing premature wear, and grinding the gears, do not shift the transfer case into 4L while the vehicle is moving faster than 3 mph (5 km/h).

Shifts into 4L can be made with the vehicle at a stop, or while slowly rolling about 1 to 3 mph (2 to 5 km/h).

•	Shift the automatic transmission into NEUTRAL (N), or with a manual transmission, press the clutch pedal, or shift into NEUTRAL.

•	Shift the transfer case shift lever in one continuous motion into the 4L position.

•	When in 4L do not drive faster than 45 mph. This will reduce wear and extend the life of the transfer case.

Shifting In or Out of NEUTRAL

With the vehicle running and the engine at an idle set the parking brake and apply the regular brake.
Place the transmission into NEUTRAL (N).

Shift the transfer case in one continuous motion into or out of the NEUTRAL position.

Automatic Transfer Case

The transfer case buttons are located to the left of the instrument panel cluster.

Use these switches to shift into and out of four-wheel drive.

Recommended Transfer Case Settings

Driving Conditions	Transfer Case Settings
Driving Conditions	2	AUTO 4WD	4	4	N
Normal	YES
Variable		YES
Severe			YES
Extreme				YES
Vehicle in Tow*					YES
*See Recreational Vehicle Towing for further information.

You can choose among five driving settings:

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.

Indicator lights in the switches show the current setting. 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 your vehicle to your dealer for service. An indicator light will flash while shifting. Fast flashing means the conditions are not being met to make the desired shift, typically the vehicle is going too fast, the automatic transmission is not in NEUTRAL, or the clutch pedal is not fully pressed. Slow flashing means the shift is in progress. 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.

AUTO 4WD (Automatic Four-Wheel Drive): This setting is ideal for use when road surface traction conditions are variable. When driving your vehicle in AUTO 4WD, 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.

2 (Two-Wheel Drive 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.

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.

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

4 (Four-Wheel Drive High): Use this setting when you need extra traction, such a on snowy or icy roads or in most off-road situations. This setting also engages your 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 Four-Wheel Drive Low. 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. When operating in Four-Wheel Drive Low, the gear ratio provides additional torque when compared to Four-Wheel Drive High. The transmission gear shift feel will be exaggerated.

If the SERVICE 4WD message stays on the Driver Information Center (DIC), you should take your vehicle to your dealer for service. See DIC Warnings and Messages for further information.

Shifting into Four-Wheel Drive High or AUTO 4WD (Automatic Four-Wheel Drive)

Press and release the Four-Wheel Drive High or AUTO 4WD switch. 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

Press and release the Two-Wheel Drive High switch. 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

Notice: Shifting the transfer case into Four-Wheel Drive Low while moving at speeds faster than 3 mph (5 km/h) may cause premature wear to the transfer case, and may cause the gears to grind. To avoid causing premature wear, and grinding the gears, do not shift the transfer case into Four-Wheel Drive Low while the vehicle is moving faster than 3 mph (5 km/h).

To shift to Four-Wheel Drive Low, the ignition must be in RUN 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 Drive Low is to have your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release the Four-Wheel Drive Low switch. 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.

It is typical for your vehicle to exhibit significant engagement noise and bump when shifting between Four-Wheel Drive Low and Four-Wheel Drive High ranges or from NEUTRAL (N) with the engine running.

If the Four-Wheel Drive Low switch is pressed when your vehicle is in gear and/or moving, the Four-Wheel Drive Low indicator light will flash for 30 seconds and the vehicle will not complete the shift unless it is moving less than 3 mph (5 km/h) and the transmission is in NEUTRAL (N). 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 4WD, or Two-Wheel Drive High, your vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) and the ignition in 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). Press and release the Four-Wheel Drive High, AUTO 4WD, or Two-Wheel Drive High switch. You must wait for the Four-Wheel Drive High, AUTO 4WD, or Two-Wheel Drive High indicator light to stop flashing and stay on before shifting the transmission into gear.

The transfer case may make noise and the vehicle may jerk when the transfer case is shifted between Four-Wheel Drive Low and Four-Wheel Drive High ranges or from NEUTRAL with the engine running.

If the Four-Wheel Drive high, AUTO 4WD, or Two-Wheel Drive High switch is pressed when your vehicle is in gear and/or moving, the Four-Wheel Drive High, AUTO 4WD, or Two-Wheel Drive High indicator light will flash for 30 seconds but the vehicle will not complete the shift unless it 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:

Make sure the vehicle is parked so that it will not roll.
Set the parking brake and apply the regular brake pedal.
Start the vehicle or turn the ignition to RUN.
Put the transmission in NEUTRAL (N).
Shift the transfer case to Two-Wheel Drive High.
Simultaneously press and hold the Two-Wheel Drive High and Four-Wheel Drive Low buttons for 10 seconds. The red NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete.
If the engine is running, shift the transmission to REVERSE (R) for one second, then shift the transmission to DRIVE (D) for one second, or FIRST (1) for vehicles that have a manual transmission.
Turn the engine off, by turning the key to ACCESSORY.
Place the transmission shift lever in PARK (P).
Release the parking brake prior to moving the vehicle.
Turn the ignition to LOCK.

Shifting Out of NEUTRAL

To shift out of NEUTRAL:

Set the parking brake and apply the regular brake pedal.
Turn the ignition to RUN with the engine off.
Shift the transmission to NEUTRAL (N).
Press the button for the desired transfer case shift position (Two-Wheel Drive High, Four-Wheel Drive High, AUTO 4WD, or Four-Wheel Drive Low).
After the transfer case has shifted out of NEUTRAL the red light will go out.
Release the parking brake prior to moving the vehicle.
You may 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 mode protects the transfer case from possible damage and only allows the transfer case to respond to one shift per 10 seconds. The transfer case may stay in this mode for up to three minutes.

Electronic Transfer Case

If your four-wheel-drive vehicle has the electronic transfer case, the transfer case switches are located to the left of the instrument panel cluster.

Recommended Transfer Case Settings

Driving Conditions	Transfer Case Settings
Driving Conditions	2	4	4	N
Normal	YES
Severe		YES
Extreme			YES
Vehicle in Tow*				YES
*See Recreational Vehicle Towing or Towing Your Vehicle for further information.

Use these switches to shift into and out of four-wheel drive. You can choose among three 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 your vehicle in to your dealer for service. An indicator light will flash while shifting. Fast flashing means the conditions are not being met to make the desired shift, typically the vehicle is going too fast, the automatic transmission is not in neutral, or the clutch pedal is not fully pressed. Slow flashing means the shift is in progress. 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 for driving in most street and highway situations. The front axle is not engaged in two-wheel drive.

(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.

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

4 (Four-Wheel Drive Low): This setting also engages your front axle to give you extra traction. You may never need Four-Wheel Drive Low. It sends the maximum power to all four wheels. You might choose Four-Wheel Drive Low if you were driving off-road in sand, mud or deep snow and while climbing or descending steep hills. When operating in Four-Wheel Drive Low, the gear ratio provides additional torque when compared to Four-Wheel Drive High. The transmission gear shift feel will be exaggerated.

Shifting from Two-Wheel Drive High to Four-Wheel Drive High

Press and release the Four-Wheel Drive High switch. This can be done at any speed. The front axle will lock automatically with some delay.

Shifting from Four-Wheel Drive High to Two-Wheel Drive High

Press and release the Two-Wheel Drive High switch. This can be done at any speed. The front axle will unlock automatically with some delay.

Shifting from Two-Wheel Drive High or Four-Wheel Drive High to Four-Wheel Drive Low

To shift from Two-Wheel Drive High or Four-Wheel Drive High to Four-Wheel Drive Low, the vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) for an automatic transmission, or the clutch pedal pressed for a manual transmission. The preferred method for shifting into Four-Wheel Drive Low is to have your vehicle moving 3 mph (5 km/h).

Press and release the Four-Wheel Drive Low switch. You must wait for the Four-Wheel Drive Low indicator light to stop flashing and stay on before shifting the transmission into gear or releasing the clutch pedal.

If the Four-Wheel Drive Low switch is pressed when your 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 your vehicle is moving slower than 3 mph (5 km/h) and the transmission is in NEUTRAL (N). The transfer case will shift to Four-Wheel Drive High while waiting to complete the shift.

It is normal to hear and feel your vehicle's transfer case shift into Four-Wheel Drive Low. If you shift with the vehicle stopped, the indicator light may continue to flash slowly. It may be necessary to shift the transmission momentarily into REVERSE (R) and DRIVE (D), for an automatic transmission, or REVERSE (R) and FIRST (1) for a manual transmission to make the light stop flashing.

Shifting from Four-Wheel Drive Low to Four-Wheel Drive High or Two-Wheel Drive High

To shift from Four-Wheel Drive Low to Four-Wheel Drive High or Two-Wheel Drive High, your vehicle must be stopped or moving less than 3 mph (5 km/h) with the transmission in NEUTRAL (N) for an automatic transmission or the clutch pedal pressed for a manual transmission. The preferred method for shifting out of Four-Wheel Drive Low is to have your vehicle moving 3 mph (5 km/h).

Press and release the Two-Wheel Drive High or Four-Wheel Drive High switch. You must wait for the Two-Wheel Drive High or Four-Wheel Drive High indicator light to stop flashing and stay on before shifting the transmission into gear or releasing the clutch pedal.

If the Four-Wheel Drive High switch is pressed when your vehicle is in gear, the Four-Wheel Drive High indicator light will flash for 30 seconds but the vehicle will not complete the shift unless it is moving slower than 3 mph (5 km/h) and the transmission is in NEUTRAL (N).

Shifting into NEUTRAL

To shift the transfer case to NEUTRAL, first make sure the vehicle is parked so that it will not roll:

Set the parking brake and apply the regular brake pedal.
Start the vehicle or turn the ignition to RUN.
Press the foot brake pedal and put the transmission in NEUTRAL (N).
Shift the transfer case to Two-Wheel Drive High.
Simultaneously press and hold the Two-Wheel Drive High and Four-Wheel Drive Low buttons for 10 seconds. The red NEUTRAL light will come on when the transfer case shift to NEUTRAL is complete.
Start the engine if it is not already running.
Press and hold the foot 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 that have a manual transmission. Then let out the clutch. This is to ensure the transfer case is in NEUTRAL. If not, repeat this procedure starting at Step 3.
Turn the engine off, by turning the key to ACCESSORY.
Place the transmission shift lever in PARK (P) for an automatic transmission, or FIRST (1) for vehicles that have a manual transmission.
Release the parking brake prior to moving the vehicle.
Turn the ignition to LOCK.

Shifting Out of NEUTRAL

To shift out of NEUTRAL:

Set the parking brake and press and hold the regular brake pedal.
Shift the transmission to NEUTRAL (N) for an automatic transmission, or press the clutch pedal for vehicles that have a manual transmission. Then turn the ignition to RUN with the engine off.
Press the button for the desired transfer case shift position (Two-Wheel Drive High, Four-Wheel Drive High, or Four-Wheel Drive Low).
After the transfer case has shifted out of NEUTRAL the red light will go out.
Release the parking brake prior to moving the vehicle.
You may 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 mode protects the transfer case from possible damage and only allows the transfer case to respond to one shift per 10 seconds. The transfer case may stay in this mode for up to three minutes.
After the transfer case has shifted out of NEUTRAL the red light will go out.