2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 427

Dolly Towing Front Towing (Front Wheels Off the Ground) Two-Wheel-Drive Vehicles Notice: If a two-wheel-drive vehicle is towed with the rear wheels on the ground, the transmission could be damaged. The repairs would not be covered by the vehicle warranty. Never tow the vehicle with the rear wheels on the ground. Two-wheel-drive vehicles should not be towed with the rear wheels on the ground. Two-wheel-drive transmissions have no provisions for internal lubrication while being towed. To dolly tow a two‐wheel‐drive vehicle, the vehicle must be towed with the rear wheels on the dolly. See "Rear Towing (Rear Wheels Off the Ground)" later in this section for more information. 5-51