2003 GMC Yukon Owner's Manual - Page 123

Shifting into 4LO To shift to the 4 lo position, the ignition must be in RUN and the vehicle must be stopped or moving less than 3 mph (4.8 km/h) with the transmission in NEUTRAL (N). 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 4 lo switch. You must wait for the 4LO indicator light to stop flashing and remain illuminated before shifting your transmission in gear. 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) and the ignition in RUN. 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, AUTO 4WD or 2HI switch. You must wait for the 4HI, AUTO 4WD or 2HI indicator light to stop flashing and remain illuminated before shifting your transmission into gear. Notice: Shifting the transmission into gear before the 4LO indicator light has stopped flashing could damage the transfer case. To help avoid damaging your vehicle, always wait for the 4LO indicator light to stop flashing before shifting the transmission into gear. It is typical for your vehicle to exhibit significant engagment noise and bump when shifting between 4LO and 4HI ranges or from NEUTRAL with the engine running. If the 4 lo switch 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). After 30 seconds the transfer case will return to the setting last chosen. Notice: Shifting the transmission into gear before the 4LO indicator light has stopped flashing could damage the transfer case. To help avoid damaging your vehicle, always wait for the 4LO indicator light to stop flashing before shifting the transmission into gear. It is typical for your vehicle to exhibit significant engagment noise and bump when shifting between 4LO and 4HI ranges or from NEUTRAL with the engine running. If the 4HI, AUTO 4WD or 2HI switch 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) and the transmission is in NEUTRAL (N). 2-29