2007 GMC SIERRA engine

NEUTRAL (N):In this position, your engine does
not connect with the wheels. To restart when
you are already moving, use NEUTRAL (N) only.
Also, use NEUTRAL (N) when your vehicle is
being towed.
{CAUTION:
Shifting into a drive gear while your engine
is running at high speed is dangerous.
Unless your foot is rmly on the brake
pedal, your vehicle could move very
rapidly. You could lose control and hit
people or objects. Do not shift into a
drive gear while your engine is running
at high speed.
Notice:Shifting out of PARK (P) or
NEUTRAL (N) with the engine running at high
speed may damage the transmission. The
repairs would not be covered by your warranty.
Be sure the engine is not running at high
speed when shifting your vehicle.DRIVE (D):This position is for normal driving. It
provides the best fuel economy for your vehicle. If
you need more power for passing, and you are:
Going less than about 35 mph (55 km/h),
push your 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.
DRIVE (D) 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
underLoss of Control on page 389.
Your vehicle has a shift stabilization feature that
adjusts the transmission shifting to the current
driving conditions in order to reduce rapid upshifts
and downshifts.
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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.
Your 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 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.
MANUAL MODE (M):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 your vehicle has this feature,
see Range Select Mode (Allison Transmission
®
or Hydra-Matic®6-Speed transmission) later in
this section.
THIRD (3):This position is also used for normal
driving. It reduces vehicle speed more than
DRIVE (D) without using the brakes. You might
choose THIRD (3) instead of DRIVE (D) 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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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 266for more
information.
Also see “Tow Haul Mode” underTowing a Trailer
on page 445for 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 andAutomatic Transmission Operation
on page 138for 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. See the diesel supplement for
information on Cruise Grade Braking.
Also seeTowing a Trailer on page 445for more
information.
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Four-Wheel Drive
If your vehicle has Four-Wheel Drive, you can
send the engine’s driving power to all four wheels
for extra traction. To get the most satisfaction
out of Four-Wheel Drive, you must be familiar with
its operation. Read the part that follows before
using Four-Wheel Drive. See the appropriate text
for the transfer case in your vehicle.
Notice:Driving on clean, dry pavement in
Four-Wheel-Drive High or Four-Wheel-Drive
Low for an extended period of time may cause
premature wear on your vehicle’s powertrain.
Do not drive on clean, dry pavement in
Four-Wheel-Drive High or Four-Wheel-Drive
Low for extended periods of time.
While driving on clean dry pavement and during
tight turns, you may experience vibration in
the steering system.
Front Axle Locking Feature
The front axle locks and unlocks automatically
when you shift the transfer case. Some delay for
the axle to lock or unlock is normal.
Manual Transfer Case
The transfer case shift lever is on the oor to the
right of the driver. Use this lever to shift into
and out of Four-Wheel Drive.
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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, and make the transfer case harder to
shift and run noisier.
If the transfer case shifter is in the 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 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 your
vehicle has warmed up.
While in Four-Wheel-Drive High, your vehicle
can be driven at any posted legal speed limit.
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Shifting In or Out of Four-Wheel-Drive Low
Notice:Shifting the transfer case into
Four-Wheel-Drive Low while moving at speeds
faster than 3 mph (5 km/h) may cause
premature wear to the transfer case, and may
cause the gears to grind. To avoid causing
premature wear, and grinding the gears, do not
shift the transfer case into Four-Wheel-Drive
Low while the vehicle is moving faster than
3 mph (5 km/h).
Shifting into Four-Wheel-Drive Low should be
done, if possible, with the vehicle at a slight roll,
3 mph (5 km/h) or less.
Shift the transmission into NEUTRAL (N).
{CAUTION:
Shifting the transfer case to NEUTRAL
can cause your vehicle to roll even if the
transmission is in PARK (P). 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 162.
Shifting into Four-Wheel-Drive Low with the
vehicle at a stop may be more difficult. You
may be unable to complete the shift to
Four-Wheel-Drive Low, and will end up in
NEUTRAL. This is normal, and is a function of
the gear teeth aligning in your transfer
case. When this happens, make sure the
engine is on, shift your transmission
momentarily to drive and back to NEUTRAL,
and then complete the shift.
Shift the transfer case shift lever in
one continuous motion into the
Four-Wheel-Drive Low position.
When Four-Wheel-Drive Low do not drive
faster than 45 mph. This will reduce wear
and extend the life of your transfer case.
Shifting In or Out of NEUTRAL
1. With the vehicle running and the engine at an
idle set the parking brake.
2. Place the transmission into NEUTRAL (N).
Shift the transfer case in one continuous motion
into or out of the NEUTRAL position.
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You must wait for the Four-Wheel-Drive Low
indicator light to stop ashing and remain on before
shifting your transmission in gear.
Notice:Shifting the transmission into gear
before the requested mode indicator light has
stopped ashing could damage the transfer
case. To help avoid damaging your vehicle,
always wait for the mode indicator lights
to stop ashing before shifting the
transmission into gear.
It is typical for your vehicle to exhibit signicant
engagement noise and bump when shifting
between Four-Wheel-Drive Low and
Four-Wheel-Drive High ranges or from NEUTRAL
with the engine running.
If the knob is turned to the Four-Wheel-Drive Low
position when your 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 your vehicle is moving less than 3 mph
(5 km/h) and the transmission is in NEUTRAL (N).
After 30 seconds the transfer case will shift to
Four-Wheel-Drive High mode.Shifting Out of Four-Wheel-Drive Low
To shift from Four-Wheel-Drive Low to
Four-Wheel-Drive High, or Two-Wheel-Drive High,
your vehicle must be stopped or moving less
than 3 mph (5 km/h) with the transmission
in NEUTRAL (N) and the ignition in 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, or Two-Wheel-Drive
High position. You must wait for the
Four-Wheel-Drive High, 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 requested mode indicator light has
stopped ashing could damage the transfer
case. To help avoid damaging your vehicle,
always wait for the mode indicator lights
to stop ashing before shifting the
transmission into gear.
It is typical for your vehicle to exhibit signicant
engagement noise and bump when shifting
between Four-Wheel-Drive Low and
Four-Wheel-Drive High ranges or from NEUTRAL
with the engine running.
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If the knob is turned to the Four-Wheel-Drive High,
or Two-Wheel-Drive High switch position when
your vehicle is in gear and/or moving, the
Four-Wheel-Drive High, or Two-Wheel-Drive High
indicator light will ash for 30 seconds but will
not complete the shift unless your vehicle is
moving less than 3 mph (5 km/h) and the
transmission is in NEUTRAL (N).
Shifting into NEUTRAL
To shift the transfer case to NEUTRAL do
the following:
1. Make sure the vehicle is parked so that it will
not roll.
2. Set the parking brake and press and hold the
regular brake pedal. SeeParking Brake on
page 162for more information.
3. Start the vehicle or turn the ignition to RUN.
4. Shift the transmission to NEUTRAL (N).5. Shift the transfer case to
Two-Wheel-Drive High.
6. Turn the transfer case dial clockwise to
NEUTRAL till it stops and hold it for
10 seconds. Then slowly release the dial to
the four low position. The NEUTRAL light will
come on when the transfer case shift to
NEUTRAL is complete.
7. If the engine is running, verify that the
transmission is in NEUTRAL (N) by shifting
the transmission to REVERSE (R) for
one second, then shift the transmission to
DRIVE (D) for one second.
8. Turn the ignition to ACCESSORY, which will
turn the engine off.
9. Place the transmission shift lever in PARK (P).
10. Release the parking brake prior to moving
the vehicle.
11. Turn the ignition to LOCK.
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