2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 428

Four-Wheel-Drive Vehicles { WARNING: Shifting a four-wheel-drive vehicle's transfer case into N (Neutral) can cause the vehicle to roll even if the transmission is in P (Park). The driver or others could be injured. Make sure the parking brake is firmly set before the transfer case is shifted to N (Neutral). 5. Use an adequate clamping device designed for towing to ensure that the front wheels are locked into the straight position. 6. Secure the vehicle to the dolly following the manufacturer's instructions. Use the following procedure to dolly tow a four-wheel-drive vehicle from the front: 1. Attach the dolly to the tow vehicle following the dolly manufacturer's instructions. 2. Drive the front wheels onto the dolly. 3. Shift the transmission to P (Park). 4. Firmly set the parking brake. 7. Shift the transfer case to N (Neutral). See "Shifting into Neutral" under Four-Wheel Drive on page 3‑39 for the proper procedure to select the neutral position for the vehicle. 8. Release the parking brake only after the vehicle being towed is firmly attached to the towing vehicle. 9. Turn the ignition to LOCK/OFF. After towing, see "Shifting Out of Neutral" under Four-Wheel Drive on page 3‑39. 5-52