2020 GMC SIERRA DENALI transmission

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
214 Driving and Operating
{Warning
The automatic engine Stop/Start
feature causes the engine to shut
off while the vehicle is still on. Do
not exit the vehicle before shifting
to P (Park). The vehicle may
restart and move unexpectedly.
Always shift to P (Park), and then
turn the ignition off before exiting
the vehicle.
Auto Engine Stop/Start
When the brakes are applied and
the vehicle is at a complete stop,
the engine may turn off. When
stopped, the tachometer displays
AUTO STOP. See Tachometer
0 131. When the brake pedal is
released or the accelerator pedal is
pressed, the engine will restart.
To maintain vehicle performance,
other conditions may cause the
engine to automatically restart
before the brake pedal is released. Auto Stops may not occur and/or
Auto Starts may occur because:
.
The climate control settings
require the engine to be running
to cool or heat the vehicle
interior.
. The vehicle battery charge
is low.
. The vehicle battery has recently
been disconnected.
. Minimum vehicle speed has not
been reached since the last
Auto Stop.
. The accelerator pedal is
pressed.
. The engine or transmission is
not at the required operating
temperature.
. The outside temperature is not
in the required operating range.
. The vehicle is in any gear other
than D (Drive).
. Tow/Haul Mode or other driver
modes have been selected.
. The vehicle is on a steep hill or
grade. .
The driver door has been
opened or the driver seat belt
has been unbuckled.
. The hood has been opened.
. The Auto Stop has reached the
maximum allowed time.
Auto Stop Disable Switch
If equipped, the automatic engine
Stop/Start feature can be disabled
and enabled by pressing the switch
with the
hsymbol. Auto Stop is
enabled each time you start the
vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
218 Driving and Operating
If you have to leave the vehicle with
the engine running, be sure the
vehicle is in P (Park) and the
parking brake is firmly set before
you leave it. After moving the shift
lever into P (Park), hold the regular
brake pedal down. Then, see if you
can move the shift lever away from
P (Park) without first pulling it toward
you. If you can, it means that the
shift lever was not fully locked into
P (Park).
Torque Lock
If you are parking on a hill and you
do not shift the transmission into
P (Park) properly, the weight of the
vehicle may put too much force on
the parking pawl in the
transmission. You may find it difficult
to pull the shift lever out of P (Park).
This is called torque lock. To
prevent torque lock, set the parking
brake and then shift into P (Park)
properly before you leave the
driver seat.When you are ready to drive, move
the shift lever out of P (Park) before
you release the parking brake.
If torque lock does occur, you may
need to have another vehicle push
yours a little uphill to take some of
the pressure from the parking pawl
in the transmission. You will then be
able to pull the shift lever out of
P (Park).
Shifting out of Park
This vehicle is equipped with an
electronic shift lock release system.
The system is designed to prevent
movement of the shift lever out of
P (Park), unless the brake pedal is
applied and the ignition is on or in
Service Mode.
The shift lock release is always
functional except in the case of an
uncharged or low voltage
–less
than 9 volt –battery.
If the vehicle has an uncharged or
low voltage battery, try charging or
jump starting the battery. See Jump
Starting - North America 0419. To shift out of P (Park):
1. Apply the brake pedal.
2. Release the parking brake if it is applied. See Electric Parking
Brake 0233.
3. Pull the shift lever toward you, then move it to the desired
position, and release.
If the vehicle still cannot be shifted
out of P (Park):
1. Ease the pressure on, or release the shift lever.
2. While holding the brake pedal, push the shift lever all the way
into P (Park).
3. Pull the shift lever toward you, then move it to the desired
position, and release.
If there is still a problem shifting,
have the vehicle serviced soon.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Driving and Operating 221
Automatic
Transmission
If equipped, there is an electronic
shift lever position indicator within
the instrument cluster. This display
comes on when the ignition is in
ACC/ACCESSORY, on or
service mode.
There are several different positions
for the shift lever.
SeeDriver Mode Control 0238 and
“Range Selection Mode” under
Manual Mode 0224.
P : This position locks the rear
wheels. Use P (Park) when starting
the engine because the vehicle
cannot move easily. When parked on a hill, especially
when the vehicle has a heavy load,
you might notice an increase in the
effort to shift out of P (Park). See
“Torque Lock”
underShifting Into
Park 0217.
{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. 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 0217 and
Driving Characteristics and
Towing Tips 0287.
{Warning
If equipped with four-wheel drive,
the vehicle will be free to roll if the
transfer case is in N (Neutral),
even when the shift lever is in
P (Park). You or someone else
could be seriously injured. Be
sure the transfer case is in a drive
gear —2
m, 4m, or 4n—or set the
parking brake before placing the
transfer case in N (Neutral). See
Four-Wheel Drive 0227.
R : Use this gear to back up.
Caution
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
222 Driving and Operating
To rock the vehicle back and forth to
get out of snow, ice, or sand without
damaging the transmission, seeIf
the Vehicle Is Stuck 0199.
N : In this position, the engine does
not connect with the wheels. To
restart the engine when the vehicle
is already moving, use
N (Neutral) only.
Also, use N (Neutral) when the
vehicle is being towed.
{Warning
Shifting into a drive gear while the
engine is running at high speed is
dangerous. Unless your foot is
firmly on the brake pedal, the
vehicle could move very rapidly.
You could lose control and hit
people or objects. Do not shift
into a drive gear while the engine
is running at high speed.
Caution
Shifting out of P (Park) or
N (Neutral) with the engine
running at high speed may
damage the transmission. The
repairs would not be covered by
the vehicle warranty. Be sure the
engine is not running at high
speed when shifting the vehicle.
Caution
A transmission or engine oil hot
message may display if the
automatic transmission fluid or
engine oil is too hot. Driving
under this condition can damage
the vehicle. Stop and idle the
engine to cool the engine oil or
automatic transmission fluid.
These messages will clear when
the engine oil or transmission
fluid has cooled sufficiently. D :
This position is for normal
driving. It provides the best fuel
economy. If more power is needed
for passing, press the accelerator
pedal down.
. When going less than about
55 km/h (35 mph), push the
accelerator pedal about
halfway down.
. When going about 55 km/h
(35 mph) or more, push the
accelerator all the way down.
By doing this, the vehicle shifts
down to the next gear and has
more power.
Use D (Drive) and Tow/Haul Mode
when towing a trailer, carrying a
heavy load, driving on steep hills,
or driving off-road. Shift the
transmission to a lower gear if the
transmission shifts too often.
Downshifting the transmission in
slippery road conditions could result
in skidding. See “Skidding”under
Loss of Control 0190.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Driving and Operating 223
The vehicle has a shift stabilization
feature that adjusts the transmission
shifting to the current driving
conditions in order to reduce rapid
upshifts and downshifts. This shift
stabilization feature is designed to
determine, before making an
upshift, if the engine is able to
maintain vehicle speed by analyzing
things such as vehicle speed,
throttle position, and vehicle load.
If the shift stabilization feature
determines that a current vehicle
speed cannot be maintained, the
transmission does not upshift and
instead holds the current gear.
In some cases, this could appear to
be a delayed shift, however the
transmission is operating normally.
If the engine or transmission detects
an impending hot fluid condition, the
transmission may upshift to limit
temperatures. Downshifts may also
be prevented. Normal operation
may continue unless the display
indicates there is a hot condition
and engine should be idled.The transmission uses adaptive
shift controls. The adaptive shift
control process continually
compares key shift parameters to
pre-programmed ideal shifts stored
in the transmission’s computer. The
transmission constantly makes
adjustments to improve vehicle
performance according to how the
vehicle is being used, such as with
a heavy load or when the
temperature changes. During this
adaptive shift control process,
shifting might feel different as the
transmission determines the best
settings.
When temperatures are very cold,
the transmission's gear shifting
could be delayed providing more
stable shifts until the engine warms
up. Shifts could be more noticeable
with a cold transmission. This
difference in shifting is normal.
If equipped with the 2.7L L4 engine,
engine speeds may be increased
while driving at highway speeds
while the engine is still warming up.L :
This position allows selection of
a range of gears appropriate for
current driving conditions.
If equipped, see “Range Selection
Mode” underManual Mode 0224.
Caution
Spinning the tires or holding the
vehicle in one place on a hill
using only the accelerator pedal
may damage the transmission.
The repair will not be covered by
the vehicle warranty. If the vehicle
is stuck, do not spin the tires.
When stopping on a hill, use the
brakes to hold the vehicle in
place.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
224 Driving and Operating
Manual Mode
Range Selection Mode
Range Selection Mode helps control
the vehicle's transmission and
vehicle speed while driving downhill
or towing a trailer by letting you
select a desired range of gears.
To use this feature:1. Move the shift lever to L (Manual Mode).
2. Press the plus/minus buttons on the shift lever to select the
desired range of gears for
current driving conditions.
When the shift lever is moved from
D (Drive) to L (Manual Mode), a
number displays next to the L,
indicating the current transmission
range. This number is the highest gear that
the transmission will command while
operating in L (Manual Mode). All
gears below that number are
available. As driving conditions
change, the transmission can
automatically shift to lower gears.
For example, when L5 is selected,
1 (First) through 5 (Fifth) gears are
automatically shifted by the
transmission, but 6 (Sixth) cannot be
used until the plus/minus button on
the shift lever is used to change to
the range.
When the shift lever is moved from
D (Drive) to L (Manual Mode), a
downshift may occur. The gear that
the transmission is operating in
when the shift lever is moved from
D (Drive) to L (Manual Mode)
determines if a downshift occurs.
See the following charts.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Driving and Operating 225
6-Speed Automatic TransmissionGear before shifting from
D (Drive) to L (Manual Mode) 6th 5th 4th 3rd 2nd 1st
Range after shifting from
D (Drive) to L (Manual Mode) L4 L4 L3 L2 L2 L1
8-Speed Automatic Transmission Gear before
shifting from
D (Drive) to
L (Manual Mode) 8th 7th 6th 5th 4th 3rd 2nd 1st
Range after
shifting from
D (Drive) to
L (Manual Mode) –
Tow/Haul not
engaged L6 L6 L5 L4 L3 L3 L2 L1
Range after
shifting from
D (Drive) to
L (Manual Mode) –
Tow/Haul engaged L6 L5 L4 L3 L3 L3 L2 L1

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
226 Driving and Operating
10-Speed Automatic TransmissionGear before shifting from D (Drive) to
L (Manual Mode) 10th 9th 8th 7th 6th 5th 4th 3rd 2nd 1st
Range after shifting from D (Drive) to
L (Manual Mode) - Tow/Haul not engaged L7 L7 L7 L6 L5 L4 L3 L3 L2 L1
Range after shifting from D (Drive) to
L (Manual Mode) - Tow/Haul engaged L7 L7 L6 L5 L4 L3 L3 L3 L2 L1
Grade Braking is not available when
Range Selection Mode is active.
See Tow/Haul Mode 0227.
While using Range Selection Mode,
cruise control and the Tow/Haul
Mode can be used.
If the vehicle has an exhaust brake,
it can also be used, but will not
automatically downshift the
transmission. See “Exhaust Brake”
in the Duramax diesel supplement.
Caution
Spinning the tires or holding the
vehicle in one place on a hill
using only the accelerator pedal
may damage the transmission.
The repair will not be covered by
the vehicle warranty. If the vehicle
is stuck, do not spin the tires.
When stopping on a hill, use the
brakes to hold the vehicle in
place.
Low Traction Mode
If equipped, Low Traction Mode
assists in vehicle acceleration when
road conditions are slippery, such
as with ice or snow. While the
vehicle is at a stop, select L2 using
Range Selection Mode. This will
limit torque to the wheels and help
prevent the tires from spinning.