Drive Systems; Four-Wheel Drive - GMC Sierra 2015 Owner's Manual

On vehicles with a gasoline engine,
to disable or enable Tow/Haul
Grade Braking within the current
ignition key cycle, press and hold
the Tow/Haul button for
five seconds. When the button is
released, the requested mode
change is made. A DIC message is
displayed. See Transmission
Messages on page 5-43.
On vehicles with a diesel engine,
Tow/Haul Mode Grade Braking can
be enabled or disabled by pressing
the Tow/Haul Mode button. Use the
exhaust brake and Tow/Haul Mode
for maximum grade braking.
See Towing Equipment on
page 9-86.
For other forms of grade braking,
see Automatic Transmission on
page 9-33 and Cruise Control on
page 9-53.

Drive Systems

Four-Wheel Drive

If equipped, four-wheel drive
engages the front axle for extra
traction. Read the appropriate
section for transfer case operation
before using.
Caution
Do not drive on clean, dry
pavement in 4 and 4 (if
equipped) for an extended period
of time. These conditions may
cause premature wear on the
vehicle s powertrain.
Driving on clean, dry pavement in
four-wheel drive may:
Cause a vibration to be felt in
the steering system.
Cause tires to wear faster.
Make the transfer case harder to
shift, and cause it to run noisier.
Driving and Operating
Warning
Shifting the transfer case to
N (Neutral) can cause the vehicle
to roll even if the transmission is
in P (Park). You or someone else
could be seriously injured. Be
sure to set the parking brake
before placing the transfer case in
N (Neutral). See Parking Brake on
page 9-48.
Caution
Extended high-speed operation in
4 may damage or shorten the
life of the drivetrain.
Engagement noise and bump when
shifting between 4 and 4 or from
N (Neutral), with the engine running,
is normal.
9-39