transmission GMC YUKON 2009 User Guide

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.
The vehicle’s transmission uses adaptive shift controls.
Adaptive shift controls continually compares key shift
parameters to pre-programmed ideal shifts stored in the
transmissions 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 Hydra-Matic
®
6-Speed 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.M (Manual Mode):This position is available on
vehicles with the Hydra-Matic
®6-Speed transmission.
It lets drivers select the range of gears appropriate
for current driving conditions. If the vehicle has
this feature, see Range Select Mode (Hydra-Matic
®
6-Speed transmission) later in this section.
3 (Third):This position is also used for normal driving.
It reduces vehicle speed more than D (Drive) without
using the brakes. You might choose 3 (Third) instead of
D (Drive) when driving on hilly, winding roads, when
towing a trailer, so there is less shifting between gears
and when going down a steep hill.
2 (Second):This position reduces vehicle speed even
more than 3 (Third) without using the brakes. You can
use 2 (Second) on hills. It can help control vehicle speed
as you go down steep mountain roads, but then you
would also want to use the brakes off and on.
If you manually select 2 (Second) in an automatic
transmission, the transmission will start in second gear.
You can use this feature for reducing the speed of the
rear wheels when you are trying to start the vehicle from
a stop on slippery road surfaces.
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1 (First):For the Hydra-Matic®4-Speed transmission
this position reduces vehicle speed even more than
2 (Second) without using the brakes. You can use it on
very steep hills, or in deep snow or mud. If the shift
lever is put in 1 (First) while the vehicle is moving
forward, the transmission does not shift into rst gear
until the vehicle is going slowly enough.
For a Hydra-Matic
®6-Speed transmission, this position
reduces vehicle speed without using the brakes. You can
use it for major/severe downgrades and off-road driving
where the vehicle would otherwise accelerate due to
steepness of grade. When you shift to 1 (First) it provides
the lowest gear appropriate to the vehicle’s current road
speed and continues to downshift as the vehicle slows,
eventually downshifting to 1 (First) gear.
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.
Range Selection Mode (Hydra-Matic®
6-Speed Transmission)
The vehicle may have a Range Selection Mode. The
Range Selection Mode helps control the vehicle’s
transmission and vehicle speed while driving down hill
or towing a trailer by letting you select a desired range
of gears.
To use this feature, do the following:
1. Move the shift lever to M (Manual Mode).
2. Press the plus/minus buttons, located on the
steering column shift lever, to select the desired
range of gears for the current driving conditions.Base trim shown (uplevel similar)
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When M (Manual Mode) is selected a number displays
next to the M, indicating the current gear.
This number 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.
Grade Braking is not available when Range Selection
Mode is active. SeeTow/Haul Mode on page 2-35
While using Range Selection Mode, cruise control and
the Tow/Haul mode can be used.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.
Low Traction Mode
If the vehicle has the Hydra-Matic®6-Speed Automatic
Transmission, it has a Low Traction Mode that assists
in vehicle acceleration when road conditions are
slippery, such as with ice or snow. While the vehicle is
at a stop, select the second gear range using Range
Selection Mode. This will limit torque to the wheels after
it detects wheel slip, preventing the tires from spinning.
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Grade Braking (Hydra-Matic®6-Speed
Automatic Transmission)
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 andAutomatic
Transmission Operation on page 2-29for 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 truck is on a downhill grade and the
driver desires to slow the vehicle by pressing the brake.
Also seeTowing a Trailer on page 4-52for more
information.
Cruise Grade Braking (Hydra-Matic®
6-Speed Automatic Transmission)
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.
SeeAutomatic Transmission Operation on page 2-29.
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2m(Two-Wheel Drive High):This setting is used for
driving in most street and highway situations. The
front axle is not engaged in two-wheel drive. This setting
also provides the best fuel economy.
AUTO (Automatic Four-Wheel Drive):This setting is
ideal for use when road surface traction conditions are
variable. When driving your vehicle in AUTO, the front
axle is engaged, but the vehicle’s power is primarily sent
to the rear wheels. When the vehicle’s software
determines a need for more traction, the system will
transfer more power to the front wheels. Driving in this
mode results in slightly lower fuel economy than
Two-Wheel Drive High.
4
m(Four-Wheel Drive High):Use the four-wheel high
position when you need extra traction, such as on snowy
or icy roads or in most off-road situations. This setting
also engages your front axle to help drive the vehicle.
This is the best setting to use when plowing snow.
4
n(Four-Wheel Drive Low):This setting also engages
the front axle and delivers extra torque. You may never
need this setting. It sends maximum power to all four
wheels. You might choose Four-Wheel Drive Low if you
are driving off-road in deep sand, deep mud, deep snow,
and while climbing or descending steep hills.
The vehicle has StabiliTrak
®. Shifting into
Four-Wheel-Drive Low will turn Traction Control and
StabiliTrak
®off. SeeStabiliTrak®System on page 4-6.
{CAUTION:
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 2-42.
N (Neutral):Shift the vehicle’s transfer case to
N (Neutral) only when towing the vehicle. See
Recreational Vehicle Towing on page 4-44orTowing
Your Vehicle on page 4-44for more information.
If the SERVICE 4 WHEEL DRIVE message stays on,
you should take the vehicle to your dealer/retailer
for service. See “SERVICE 4 WHEEL DRIVE message”
underDIC Warnings and Messages on page 3-64.
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Shifting Into Four-Wheel Drive High or
AUTO (Automatic Four-Wheel Drive)
Turn the knob to the Four-Wheel High or AUTO position.
This can be done at any speed, except when shifting
from Four-Wheel Drive Low. The indicator light will ash
while shifting. It will remain on when the shift is
completed.
Shifting Into Two-Wheel Drive High
Turn the knob to the Two-Wheel High position. This
can be done at any speed, except when shifting
from Four-Wheel Drive Low.
See shifting out of Four-Wheel Drive Low later in this
section for more information.
Shifting Into Four-Wheel Drive Low
When Four-Wheel Low is engaged, vehicle speed
should be kept below 45 mph (72 km/h). Extended
high-speed operation in 4L may damage or shorten
the life of the drivetrain.
To shift to the Four-Wheel Drive Low position, the ignition
must be in ON/RUN and the vehicle must be stopped or
moving less than 3 mph (5 km/h) with the transmissionin N (Neutral). The preferred method for shifting into
Four-Wheel Drive Low is to have the vehicle moving
1 to 2 mph (1.6 to 3.2 km/h). Turn the knob to the
Four-Wheel Drive Low position. You must wait for the
Four-Wheel Drive Low indicator light to stop ashing and
remain on before shifting the transmission into gear.
Notice:Shifting the transmission into gear before
the Four-Wheel Drive Low indicator light has
stopped ashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
ashing before shifting the transmission into gear.
The vehicle may have signicant engagement noise
and bump when shifting between Four-Wheel Drive Low
and Four-Wheel Drive High ranges or from N (Neutral)
while the engine is running.
If the knob is turned to the Four-Wheel Drive Low
position when the vehicle is in gear and/or moving, the
Four-Wheel Drive Low indicator light will ash for
30 seconds and not complete the shift unless the vehicle
is moving less than 3 mph (5 km/h) and the transmission
is in N (Neutral). After 30 seconds the transfer case
will shift to Four-Wheel Drive High mode.
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Shifting Out of Four-Wheel Drive Low
To shift from Four-Wheel Drive Low to Four-Wheel Drive
High, AUTO, or Two-Wheel Drive High, the vehicle must
be stopped or moving less than 3 mph (5 km/h) with the
transmission in N (Neutral) and the ignition in ON/RUN.
The preferred method for shifting out of Four-Wheel
Drive Low is to have your vehicle moving 1 to 2 mph
(1.6 to 3.2 km/h). Turn the knob to the Four-Wheel Drive
High, AUTO, or Two-Wheel Drive High position. You
must wait for the Four-Wheel Drive High, AUTO, or
Two-Wheel Drive High indicator light to stop ashing and
remain on before shifting the transmission into gear.
Notice:Shifting the transmission into gear before
the Four-Wheel Drive Low indicator light has
stopped ashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
ashing before shifting the transmission into gear.
The vehicle may have signicant engagement noise
and bump when shifting between Four-Wheel Drive Low
and Four-Wheel Drive High ranges or from N (Neutral)
while the engine is running.
If the knob is turned to the Four-Wheel Drive High,
AUTO, or Two-Wheel Drive High switch position when
the vehicle is in gear and/or moving, the Four-Wheel
Drive High, AUTO or Two-Wheel Drive High indicator
light will ash for 30 seconds but will not complete
the shift unless the vehicle is moving less than
3 mph (5 km/h) and the transmission is in N (Neutral).
Shifting into Neutral
To shift the transfer case to N (Neutral) do the following:
1. Make sure the vehicle is parked so that it will
not roll.
2. Set the parking brake and apply the regular brake
pedal. SeeParking Brake on page 2-42for more
information.
3. Start the vehicle or turn the ignition to ON/RUN.
4. Put the transmission in N (Neutral).
5. Shift the transfer case to Two-Wheel Drive High.
6. Turn the transfer case dial clockwise to N (Neutral)
until it stops and hold it there until the N (Neutral)
light starts blinking. This will take at least
10 seconds. Then slowly release the dial to the
Four-Wheel Drive Low position. The N (Neutral) light
will come on when the transfer case shift to
N (Neutral) is complete.
7. If the engine is running, verify that the transfer case
is in N (Neutral) by shifting the transmission to
R (Reverse) for one second, then shift the
transmission to D (Drive) for one second.
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8. Turn the ignition to ACC/ACCESSORY, which will
turn the engine off.
9. Place the transmission shift lever in P (Park).
10. Release the parking brake prior to moving the
vehicle.
11. Turn the ignition to LOCK/OFF.
Shifting Out of Neutral
To shift out of N Neutral do the following:
1. Set the parking brake and apply the regular brake
pedal.
2. Turn the ignition to ON/RUN with the engine off,
and shift the transmission to N (Neutral).
3. Turn the transfer case dial to the desired transfer
case shift position (Two-Wheel Drive High,
Four-Wheel Drive High, AUTO).
After the transfer case has shifted out of N (Neutral),
the N (Neutral) light will go out.4. Release the parking brake prior to moving the
vehicle.
Notice:Shifting the transmission into gear before
the Four-Wheel Drive Low indicator light has
stopped ashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
ashing before shifting the transmission into gear.
5. Start the engine and shift the transmission to
the desired position.
Excessively shifting the transfer case into or out of
the different modes may cause the transfer case to enter
the shift protection mode. This will protect the transfer
case from possible damage and will only allow the
transfer case to respond to one shift per 10 seconds.
The transfer case may stay in this mode for up to
three minutes.
2-41

If you have to leave the vehicle with the engine running,
be sure your vehicle is in P (Park) and the parking brake
is rmly set before you leave it. After you move 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 rst 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 your
transmission into P (Park) properly, the weight of the
vehicle may put too much force on the parking pawl in
the transmission. You may nd 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.
To nd out how, seeShifting Into Park on page 2-44.
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, then
you will 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.
SeeJump Starting on page 5-45for more information.
To shift out of P (Park) use the following:
1. Apply the brake pedal.
2. Move the shift lever to the desired position.
If you still are unable to shift out of P (Park):
1. Ease the pressure on the shift lever.
2. While holding down the brake pedal, press the shift
lever all the way into P (Park).
3. Move the shift lever to the desired position.
If you are still having a problem shifting, then have the
vehicle serviced soon.
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{CAUTION:
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 rmly 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).
{CAUTION:
Four-wheel drive vehicles with the transfer case
in N (Neutral) will allow the vehicle to roll, even
if the automatic transmission shift lever is in
P (Park). So, be sure the transfer case is in a
drive gear — not in N (Neutral). Always set the
parking brake.Follow the proper steps to be sure the vehicle will not
move. SeeShifting Into Park on page 2-44.
If pulling a trailer, seeTowing a Trailer on page 4-52.
Mirrors
Manual Rearview Mirror
Hold the inside rearview mirror in the center to move it
for a clearer view behind your vehicle. Adjust the
mirror to avoid glare from the headlamps behind you.
Push the tab forward for daytime use and pull it for
nighttime use.
Automatic Dimming Rearview Mirror
The vehicle may have an automatic dimming rearview
mirror.
Vehicles with OnStar
®have three additional control
buttons for the OnStar®system. See your dealer/retailer
for more information about OnStar®and how to
subscribe to it. SeeOnStar®System on page 2-64for
more information about the services OnStar®provides.
2-48