GMC 2007 Envoy Denali Owner's Manual page 357

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.
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 122 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 122.
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