2010 GMC YUKON XL towing

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.
3-34

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.
3-37

Tow/Haul Mode
The vehicle has a Tow/Haul mode. The selector button
is located on the end of the column shift lever. You can
use this feature to assist when towing or hauling a
heavy load or if there is a need to charge a battery
installed in a trailer. SeeTowing a Trailer
on page 5‑49for more information.
When Tow/Haul mode is
selected the Tow/Haul
indicator light will
come on.
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 5‑48.
3-39

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

To release the parking brake, hold the regular brake
pedal down, then push down momentarily on the
parking brake pedal until you feel the pedal release.
Slowly pull your foot up off the park brake pedal. If the
parking brake is not released when you begin to drive,
the brake system warning light will flash and a chime
will sound warning you that the parking brake is still on.
If you are towing a trailer and are parking on a hill, see
Towing a Trailer on page 5‑49.
Shifting Into Park
{WARNING:
It can be 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. 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, use the steps that follow.
If you have a four-wheel drive transfer case with
a N (Neutral) position, and the transfer case is in(Continued)
WARNING: (Continued)
N (Neutral), the vehicle will be free to roll, even
if the shift lever is in P (Park). So, be sure the
transfer case is in a drive gear—not in
N (Neutral). If you are pulling a trailer, see Towing
a Trailer
on page 5‑49. Always set the parking
brake.
1. Hold the brake pedal down, then set the parking brake.
See Parking Brake
on page 3‑48for more
information.
2. Move the shift lever into the P (Park) position by pulling the shift lever toward you and moving it up
as far as it will go.
3. Be sure the transfer case is in a drive gear —not
in N (Neutral).
4. Turn the ignition key to LOCK/OFF.
5. Remove the key and take it with you. If you can leave the vehicle with the ignition key in your hand,
the vehicle is in P (Park).
3-49

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 3‑52.
{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.
(Continued)
WARNING: (Continued)
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).
{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 may 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. See Shifting Into Park on page 3‑49.
If pulling a trailer, see Towing a Trailer on page 5‑49.
3-53