2003 GMC Sierra 1500 Pickup Owner's Manual - Page 335

Four-Wheel-Drive Vehicles 4. Shift the transfer case to NEUTRAL. See Four-wheel Drive on page 2-35 for the proper procedure to select the neutral position for your vehicle. 5. Release the parking brake only after the vehicle being towed is firmly attached to the towing vehicle. 6. Turn the ignition off. Use the following procedure to tow your vehicle: 1. Firmly set the parking brake. 2. Shift an automatic transmission to PARK (P), or a manual transmission to FIRST (1). 3. Securely attach the vehicle being towed to the tow vehicle. Shifting a four-wheel-drive vehicle's transfer case into NEUTRAL can cause your vehicle to roll even if the transmissionis in Park (P)for an automatic transmission, or if your vehicle is in gear, for a manual transmission. You or others could be injured.Make sure the parking brake is firmly set before you shift transfer the case to NEUTRAL. 4-54