2007 GMC Sierra 1500 Pickup Owner's Manual - Page 160

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. 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 your 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. 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). 160