GMC 2007 Yukon XL Owner's Manual page 402

Four-Wheel-Drive Vehicles
Use the following procedure to tow your vehicle:
1. Shift the transmission to PARK (P).
2. Turn the engine off, but leave the ignition on.
3. Firmly set the parking brake.
4. Securely attach the vehicle being towed to the
tow vehicle.
402
CAUTION:
{
Shifting a four-wheel-drive vehicle's
transfer case into NEUTRAL can cause
your vehicle to roll even if the
transmission is in PARK (P). You or
others could be injured. Make sure the
parking brake is firmly set before you shift
the transfer case to NEUTRAL.
5. Shift the transfer case to NEUTRAL (N). See
Four-Wheel Drive on page 146 for the proper
procedure to select the NEUTRAL (N)
position for your vehicle.
6. Release the parking brake only after the
vehicle being towed is firmly attached to
the towing vehicle.
7. Turn the ignition off.