transmission GMC SIERRA 2010 User Guide

Automatic Transmission Operation
If the vehicle is a Two-mode Hybrid, see the Two-mode
Hybrid manual for more information.
Vehicles with an automatic transmission have 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
Heavy Duty 6-Speed Automatic Transmission Shown (Light Duty 6 Speed 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 3‑51for more
information.
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{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). SeeShifting Into
Park
on page 3‑51. If you are pulling a trailer,
see Towing a Trailer on page 5‑50.
{WARNING:
If you have Four-Wheel Drive, the vehicle
will be free to roll —even if the shift lever is in
P (Park) —if the transfer case is in Neutral.
So, 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 Neutral.
See Shifting Into Park on page 3‑51.
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 5‑28.
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N (Neutral) :In this position, the engine does not
connect with the wheels. To restart when you are
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. 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 5‑10.
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.
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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 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 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 Allison
Transmission
®and 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 Allison Transmission
®or 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
(Allison Transmission
®or 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 first gear
until the vehicle is going slowly enough.
For an Allison Transmission
®or 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 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 (Allison®or
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.
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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 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 3‑34.
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 your vehicle has the Allison Transmission®, or the
Hydra-Matic®6-Speed Automatic Transmission,
it has a Low Traction Mode that can assist 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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Tow/Haul Mode
Vehicles with an automatic transmission have 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.
The selector button is located on the end of the shift
lever. Turn the tow/haul on and off by pressing the
button. When the tow/haul is on, a light on the
instrument panel cluster will come on.
SeeTow/Haul Mode Light
on page 4‑49for more
information. Also see Tow Haul Mode under
Towing a Trailer
on
page 5‑50for more information.
Tow/Haul Mode (Allison Transmission®
or Hydra-Matic®6-Speed Automatic
Transmission)
Vehicles with an Allison or Hydra-Matic®6-speed
automatic transmission®have 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.
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Turn the tow/haul mode on and off by pressing the
button, located on the end of the shift lever. When the
tow/haul is on, a light on the instrument panel cluster
will come on.
SeeTow/Haul Mode Light
on page 4‑49for more
information.
Also see “Tow Haul Mode” underTowing a Trailer
on
page 5‑50for more information.
Grade Braking (Allison Transmission®
or 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 3‑28for
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 5‑50for more
information.
Cruise Grade Braking (Allison
Transmission®or 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 3‑28.
3-35

A parking brake symbol
is located next to the
N (Neutral) symbol as a
reminder to set the
parking brake before
shifting the transfer case
into N (Neutral).
{WARNING:
Shifting the transfer case to 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 Neutral. SeeParking
Brake on page 3‑50. N (Neutral) :
Shift to this setting only when the vehicle
needs to be towed. See Recreational Vehicle Towing
on
page 5‑43or Towing Your Vehicle on page 5‑43.
2
m(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.
4
m(Four-Wheel-Drive High): Use this setting when
you need extra traction, such as on snowy or icy roads
or in most off-road situations. This setting also engages
the front axle to help drive your vehicle. This is the best
setting to use when plowing snow.
You can shift from Two-Wheel-Drive High to
Four-Wheel-Drive High or Four-Wheel-Drive High to
Two-Wheel-Drive High while the vehicle is moving.
In extremely cold weather, it may be necessary to stop
or slow the vehicle to shift into Four-Wheel-Drive High.
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When Using the Manual Transfer Case
.Shifting should be made using quick motions.
Shifting slowly may make it more difficult to shift.
.You may notice that it is harder to shift when the
vehicle is cold. After the vehicle warms up the
shifting will return to normal.
.While in Four-Wheel High or Four-Wheel-Drive
Low you may experience reduced fuel economy.
.Avoid driving in Four-Wheel Drive on clean, dry
pavement. It may cause your tires to wear faster,
make the transfer case harder to shift, and run
noisier.
.If the transfer case shifter is in the N (Neutral)
position and you have difficulty reaching the
selected transfer case mode, with the engine
running, shift the transmission momentarily to drive
and then back to N (Neutral). This will realign the
gear teeth in the transfer case and allow you to
complete the shift.
Shifting from Two-Wheel-Drive High to
Four-Wheel-Drive High
.Shifts between Two-Wheel-Drive High and
Four-Wheel-Drive High can be made at any
vehicle speed.
.Shift the transfer case lever in one continuous
motion into either the Four-Wheel-Drive High or
Two-Wheel-Drive High position.
.In extremely cold weather, it may be necessary
to slow or stop the vehicle to shift into
Four-Wheel-Drive High until the vehicle has
warmed up.
.While in Four-Wheel-Drive High, the vehicle can be
driven at any posted legal speed limit.
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