transmission GMC YUKON DENALI 2010 User Guide

Automatic Transmission Operation
The vehicle has a Hydra-Matic®6L80 automatic
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 3‑37for more information.
{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 3‑37. If you are pulling a trailer,
see Towing a Trailer on page 5‑42.
3-30

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.
N (Neutral) : 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. Notice:
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.
D (Drive) : This position is for normal driving. It provides
the best fuel economy for the vehicle. If you need more
power for passing, and you are:
.Going less than about 35 mph (55 km/h), push the
accelerator pedal about halfway down.
.Going about 35 mph (55 km/h) or more, push the
accelerator all the way down.
D (Drive) can be used when towing a trailer, carrying a
heavy load, driving on steep hills, or for off-road driving.
You may want to shift the transmission to a lower gear
selection if the transmission shifts too often.
Downshifting the transmission in slippery road
conditions could result in skidding, see “Skidding”
under Loss of Control on page 5‑11.
3-31

When temperatures are very cold, the Hydra-Matic®
Automatic Transmission's gear shifting may be delayed
providing more stable shifts until the engine warms up.
Shifts may be more noticeable with a cold transmission.
This difference in shifting is normal.
M (Manual Mode) :This position lets drivers select
the range of gears appropriate for current driving
conditions. See Range Selection Mode later in this
section.
Notice: 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 you are stuck,
do not spin the tires. When stopping on a hill, use
the brakes to hold the vehicle in place.
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 will
be able to maintain vehicle speed by analyzing things
such as throttle position, vehicle load, and hill grade. 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 may appear to be a delayed shift,
however the transmission is operating normally.
The vehicle's transmission uses adaptive shift controls.
Adaptive shift controls continually compares key shift
parameters to pre‐programmed ideal shift conditions
stored in the transmissions computer. The transmission
constantly makes adjustments to improve vehicle
performance according to the way the vehicle is being
used, such as with a heavy load. During this adaptive
shift controls process, some shifts may feel different as
the transmission determines the best settings for a
particular shift.
3-32

Range Selection Mode
On vehicles with a Range Selection Mode, this feature
may be used to control the vehicle's transmission.
To use this feature, do the following:1. Move the shift lever to the M (Manual Mode).
2. Press the plus/minus button, to upshift or downshift selecting the desired range of gears for current
driving conditions. When in M (Manual Mode) a number displays next
to the M, indicating the current gear that has been
selected. The number displayed in the gear indicator is
the highest gear that can be used. However, the vehicle
can automatically shift to lower gears as it adjusts to
driving conditions. This means that all gears below
that number are available. When 5 (Fifth) is selected,
1 (First) through 5 (Fifth) gears are automatically shifted
by the vehicle, but 6 (Sixth) cannot be used until the
plus/minus button located on the steering column lever
is used to change to the gear.
Range Selection Mode controls the vehicle and engine
speed while driving down a hill or towing a trailer,
by allowing you to select a desired range of gears.
Grade Braking is not available when the Range
Selection Mode is active. See
Tow/Haul Mode
on
page 3‑34for more information.
While using the Range Selection Mode, Cruise Control
and the Tow/Haul mode can be used.
3-33

Tow/Haul Mode
The vehicle has a tow/haul mode. The tow/haul mode
adjusts the transmission shift pattern to reduce shift
cycling, providing increased performance, vehicle
control, and transmission cooling when towing or
hauling heavy loads.Press the button located on the end of the shift lever to
turn the tow/haul on or off. When the tow/haul is on, a
light on the instrument panel cluster will come on.
See
Tow/Haul Mode Light
on page 4‑40for more
information.
Also see “Tow Haul Mode” underTowing a Trailer
on
page 5‑42for more information.
The tow/haul mode works with the Autoride
®feature,
if the vehicle has this, to enhance the ride when
trailering or with a loaded vehicle. See Autoride
®on
page 5‑41.
3-34

Grade Braking
The Grade Braking shift modes can be activated by
pressing the button on the end of the shift control lever.
While in Range Selection Mode , Grade Braking is
deactivated allowing the driver to select a desired range
of gears.
Grade Braking is only active while the Tow/Haul Mode
is selected and you are not in the Range Selection
Mode. See“Tow/Haul Mode listed previously and
Automatic Transmission Operation
on page 3‑30for
more information on the Range Selection Mode. Grade
Braking assists in maintaining desired vehicle speeds
when driving on downhill grades by automatically
implementing a shift schedule that utilizes the engine
and transmission to slow the vehicle. This reduces wear
on the braking system and increases control of the
vehicle. Grade Braking monitors vehicle speed,
acceleration, engine torque and brake pedal usage.
Using this information, it detects when the vehicle is on
a downhill grade and the driver desires to slow the
vehicle by pressing the brake.
Also see Towing a Trailer
on page 5‑42for more
information.
Cruise Grade Braking
Cruise Grade Braking assists when driving on a
downhill grade. It maintains vehicle speed by
automatically implementing a shift schedule that uses
the engine and the transmission to slow the vehicle.
Cruise Grade Braking operates while Cruise Control is
engaged in Tow/Haul mode to assist in maintaining
vehicle speed under loaded vehicle conditions.
It utilizes vehicle acceleration and deviation from
desired speed to determine the correct gear for the
operating condition. If vehicle speed is above the
desired speed the transmission will downshift to slow
the vehicle. If vehicle speed is near or below desired
speed the trans will upshift, allowing vehicle speed to
increase.
While in the Range Select Mode (RSM) mode, cruise
grade braking is not available.
See Automatic Transmission Operation on page 3‑30.
3-35

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 can put too much force on the parking pawl in
the transmission. It might be 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. To find out how, seeShifting Into Park
on
page 3‑37.
When you are ready to drive, move the shift lever out
of P (Park) before releasing the parking brake.
If torque lock does occur, you might need to have
another vehicle push yours a little uphill to take some of
the pressure from the parking pawl in the transmission.
Then you should 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 shift lock release is designed to:
.Prevent ignition key removal unless the shift lever
is in P (Park) with the shift lever button fully
released, and
.Prevent movement of the shift lever out of
P (Park), unless the ignition is in ON/RUN or
ACC/ACCESSORY and the regular brake pedal
is applied.
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 battery or a battery with
low voltage, try charging or jump starting the battery.
See Jump Starting
on page 6‑42for more information.
3-38

Running the Vehicle While Parked
It is better not to park with the engine running. But if you
ever have to, here are some things to know.
{WARNING:
Idling a vehicle in an enclosed area with poor
ventilation is dangerous. Engine exhaust may
enter the vehicle. Engine exhaust contains
Carbon Monoxide (CO) which cannot be seen or
smelled. It can cause unconsciousness and
even death. Never run the engine in an enclosed
area that has no fresh air ventilation. For more
information, seeEngine Exhaust on page 3‑40.
{WARNING:
It can be dangerous to get out of the vehicle if the
automatic transmission 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).
Follow the proper steps to be sure the vehicle will not
move. See Shifting Into Park on page 3‑37.
If parking on a hill and pulling a trailer, see Towing a
Trailer on page 5‑42.
3-41

The rear window wiper/washer will not operate if the
liftgate or liftglass is open or ajar. If the liftgate or
liftglass is opened while the rear wiper is on, the wiper
will return to the parked position and stop.
Cruise Control
{WARNING:
Cruise control can be dangerous where you
cannot drive safely at a steady speed. So, do not
use the cruise control on winding roads or in
heavy traffic.
Cruise control can be dangerous on slippery
roads. On such roads, fast changes in tire traction
can cause excessive wheel slip, and you could
lose control. Do not use cruise control on slippery
roads.With cruise control, a speed of about 40 km/h (25 mph)
or more can be maintained without keeping your foot on
the accelerator. Cruise control does not work at speeds
below about 40 km/h (25 mph).
When the brakes are applied, the cruise control
turns off.
For vehicles with an Allison
®or Hydra‐Matic 6‐speed
automatic transmission, see “Grade Braking and Cruise
Grade Braking (Allison Transmission) under Tow/Haul
Mode
on page 3‑34for an explanation of how cruise
control interacts with the Range Selection Mode,
tow/haul and grade braking systems.
For vehicles with the StabiliTrak
®system, if it begins to
limit wheel spin while the cruise control is being used,
the cruise control will automatically disengage. See
StabiliTrak
®Systemon page 5‑6. When road
conditions allow the cruise control to be safely used
again, it can be turned back on.
4-8

To turn off the DRL lamps, turn the exterior lamps
control to the OFF position and then release.
For vehicles first sold in Canada, the transmission
must be in the P (Park) position, before the DRL lamps
can be turned off.
Automatic Headlamp System
When it is dark enough outside, the automatic
headlamp system turns on the headlamps at the normal
brightness, along with the taillamps, sidemarker, parking
lamps, and the instrument panel lights. The radio lights
will also be dim.
To turn off the automatic headlamp system, turn the
exterior lamps switch to the off position and then
release it. For vehicles first sold in Canada, the
transmission must be in the P (Park) position, before
the automatic headlamp system can be turned off.
The vehicle has a light sensor located on the top of the
instrument panel in the defroster grille that regulates
when the automatic headlamps turn on. Do not cover
the sensor or the headlamps will come on whenever the
ignition is on.
The system may also turn on the headlamps when
driving through a parking garage, heavy overcast
weather, or a tunnel. This is normal.There is a delay in the transition between the daytime
and nighttime operation of the Daytime Running Lamps
(DRL) and the automatic headlamp systems so that
driving under bridges or bright overhead street lights
does not affect the system. The DRL and automatic
headlamp system is only affected when the light
sensor detects a change in lighting lasting longer than
the delay.
If the vehicle is started in a dark garage, the automatic
headlamp system will come on immediately. Once the
vehicle leaves the garage, it takes approximately
one minute for the automatic headlamp system to
change to DRL if it is bright enough outside. During that
delay, the instrument panel cluster may not be as bright
as usual. Make sure the instrument panel brightness
control is in the full bright position. See
Instrument
Panel Brightness on page 4‑14.
To idle the vehicle with the automatic headlamp system
off, turn the control to the off position.
The headlamps will also stay on after you exit the
vehicle. This feature can be programmed using the
Driver Information Center (DIC). See DIC Vehicle
Customization (With DIC Buttons) on page 4‑66.
The regular headlamp system can be turned on when
needed.
4-13