Automatic Transmission Operation - GMC 2010 Sierra Denali Owner's Manual

Automatic Transmission Operation

The vehicle has a Hydra-Matic
transmission, and has an electronic shift position
indicator within the instrument panel cluster. The
electronic shift position indicator displays when the shift
lever is moved out of P (Park).
There are several different positions for the shift lever.
Light Duty 6 Speed Automatic Transmission Shown
(Heavy Duty 6 Speed Similar)
See Range Selection Mode later in this section.
P (Park) : This position locks your rear wheels. It is the
best position to use when you start the engine because
the vehicle cannot move easily.
When parked on a hill, especially when the vehicle has
a heavy load, you may notice an increase in the effort to
shift out of P (Park). See Torque Lock (Automatic
Transmission) under Shifting Into Park on page 3 35
for more information.
3-28
®
6L80 automatic
WARNING:
It is dangerous to get out of the vehicle if the shift
lever is not fully in P (Park) with the parking brake
firmly set. The vehicle can roll.
Do not leave the vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure the
vehicle will not move, even when you are on fairly
level ground, always set the parking brake and
move the shift lever to P (Park). See Shifting Into
Park on page 3 35. If you are pulling a trailer,
see Towing a Trailer on page 5 42.
R (Reverse) : Use this gear to back up.
Notice: Shifting to R (Reverse) while the vehicle is
moving forward could damage the transmission.
The repairs would not be covered by the vehicle
warranty. Shift to R (Reverse) only after the vehicle
is stopped.
To rock the vehicle back and forth to get out of snow,
ice, or sand without damaging the transmission, see If
Your Vehicle is Stuck in Sand, Mud, Ice, or Snow on
page 5 29.