2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 181

Shifting In or Out of Four-Wheel-Drive Low Notice: Shifting the transfer case into Four-Wheel-Drive Low while moving at speeds faster than 5 km/h (3 mph) 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 5 km/h (3 mph). Shifting into Four-Wheel-Drive Low should be done, if possible, with the vehicle at a slight roll, 3 mph (5 km/h) or less. . WARNING: (Continued) injured. Be sure to set the parking brake before placing the transfer case in Neutral. See Parking Brake on page 3‑54. . Shift the transmission into N (Neutral). { WARNING: . Shifting into Four-Wheel-Drive Low with the vehicle at a stop may be more difficult. You may be unable to complete the shift to Four-Wheel-Drive Low, and the transfer case will end up in N (Neutral). This is normal, and is a function of the gear teeth aligning in the transfer case. When this happens, make sure the engine is on, shift the transmission momentarily to D (Drive) and back to N (Neutral), and then complete the transfer case shift. Shift the transfer case shift lever in one continuous motion into the Four-Wheel-Drive Low position. When Four-Wheel-Drive Low do not drive faster than 45 mph. This will reduce wear and extend the life of your transfer case. 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 (Continued) . 3-43