transmission GMC YUKON 2010 User Guide

Active Fuel Management™
Vehicles with V8 engines may have Active Fuel
Management™. This system allows the engine to
operate on either all or half of its cylinders, depending
on the driving conditions.
When less power is required, such as cruising at a
constant vehicle speed, the system will operate in the
half cylinder mode, allowing the vehicle to achieve
better fuel economy. When greater power demands
are required, such as accelerating from a stop, passing,
or merging onto a freeway, the system will maintain
full-cylinder operation.
If the vehicle has an Active Fuel Management™
indicator, seeDIC Operation and Displays (With DIC
Buttons)
on page 4‑48or DIC Operation and Displays
(Without DIC Buttons)on page 4‑55for more
information on using this display .
Automatic Transmission Operation
If the vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
If the vehicle is has an automatic transmission, it has an
electronic shift position indicator within the instrument
panel cluster. This display comes on when the ignition
key is turned to the ON/RUN position.
There are several different positions for the shift lever.
Hydra-Matic®4-Speed
Automatic Transmission
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Heavy Duty 6-Speed Automatic Transmission Shown(Light Duty Similar)
See “Range Selection Mode” later in this section.
P (Park): This position locks the rear wheels. It is the
best position to use 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 (Automatic Transmission)
under Shifting Into Park
on page 3‑49for 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 3‑49. If you are pulling a trailer,
see Towing a Trailer on page 5‑49.
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{WARNING:
If the vehicle has a four-wheel drive transfer
case with a N (Neutral) position, and the transfer
case is in N (Neutral), the vehicle will be free to
roll—even if the shift lever is in P (Park). Be sure
the transfer case is in a drive gear, Two-Wheel
Drive High or Four-Wheel Drive High or
Four-Wheel Drive Low —not in N (Neutral).
See Shifting Into Park
on page 3‑49. Always
set the parking brake.
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.
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D (Drive):This position is for normal driving. It provides
the best fuel economy. 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.
By doing this, the vehicle shifts down to the next
gear and has more power.
D (Drive) can be used when towing a trailer, carrying a
heavy load, driving on steep hills, or for off-road driving.
You might 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.
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. 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.
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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.
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 first 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)
Base trim shown (uplevel similar)
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.
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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.
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. See Tow/Haul Mode on page 3‑39. 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 and
Automatic Transmission Operation
on page 3‑33for 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 see Towing a Trailer
on page 5‑49for 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.
See Automatic Transmission Operation on page 3‑33.
3-40

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. See StabiliTrak®System on page 5‑6.
{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).
SeeParking Brake on page 3‑48.
N (Neutral): Shift the vehicle's transfer case
to N (Neutral) only when towing the vehicle.
See Recreational Vehicle Towing
on page 5‑41orTowing Your Vehicleon page 5‑41for more
information.
If the SERVICE 4 WHEEL DRIVE message stays on,
you should take the vehicle to your dealer for service.
See “SERVICE 4 WHEEL DRIVE message” underDIC
Warnings and Messages on page 4‑61.
3-42

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 flash 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 thetransmission in 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
flashing 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 flashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
flashing before shifting the transmission into gear.
The vehicle may have significant 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 flash
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.
3-43

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 flashing
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 flashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
flashing before shifting the transmission into gear. The vehicle may have significant 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 flash 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).
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