GMC 2005 Envoy Owner's Manual page 318

Four-Wheel-Drive Vehicles
Four-wheel-drive vehicles can be dinghy towed if you
follow the proper procedures. The transmission has
no provisions for internal lubrication while being towed,
so it is important that you follow all the steps listed
in this manual to dinghy tow your four-wheel-drive
vehicle.
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.
4-52
3. Firmly set the parking brake.
4. Securely attach the vehicle being towed to the
tow vehicle.
CAUTION:
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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 2-27 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.
After towing, see "Shifting Out of Neutral" under
Four-Wheel Drive on page 2-27.