GMC 2007 Sierra - Manual (Page 425)

Four-Wheel-Drive Vehicles
Use the following procedure to tow your vehicle:
1. Shift an automatic transmission to PARK (P),
or a manual transmission to FIRST (1).
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) 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 the
transfer case to NEUTRAL.
5. Shift the transfer case to NEUTRAL.
See Four-Wheel Drive on page 153 for the
proper procedure to select the neutral 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 and leave the steering
column unlocked.
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