GMC 2008 Envoy Denali Owner's Manual page 281

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.
6. Shift the transfer case to NEUTRAL (N). See
Four-Wheel Drive on page 2-29 for the proper
procedure to select the NEUTRAL (N) position for
your vehicle.
7. Release the parking brake only after the vehicle
being towed is firmly attached to the towing
vehicle.
8. Turn the ignition off.
After towing, see "Shifting Out of Neutral" under
Four-Wheel Drive on page 2-29.
Rear Towing (Rear Wheels Off
the Ground)
(Two-Wheel or Four-Wheel-Drive Vehicles)
Use the following procedure to tow your vehicle from
the rear:
1. Drive the vehicle onto the dolly.
2. Firmly set the parking brake. See Parking Brake on
page 2-33 for more information.
3. Shift the transmission in PARK (P).
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