2007 GMC SIERRA CLASSIC trailer

Mirrors......................................................... 176
Manual Rearview Mirror............................. 176
Automatic Dimming Rearview Mirror with
OnStar
®, Compass and Temperature
Display................................................... 176
Automatic Dimming Rearview Mirror with
Compass and Temperature Display........ 180
Outside Manual Mirrors............................. 183
Outside Trailer-Tow Mirrors....................... 183
Outside West Coast-Type Mirrors.............. 185
Outside Power Mirrors............................... 185
Outside Power Foldaway Mirrors............... 186
Outside Automatic Dimming Mirror............. 187
Outside Curb View Assist Mirrors.............. 187
Outside Convex Mirror............................... 188
Outside Heated Mirrors............................. 188
OnStar
®System.......................................... 189Universal Home Remote System................ 191
Universal Home Remote System
(With Three Round LED)....................... 191
Universal Home Remote System
(With One Triangular LED)..................... 192
Universal Home Remote System
Operation (With Three Round LED)....... 193
Universal Home Remote System
Operation (With One Triangular LED)..... 198
Storage Areas............................................. 202
Glove Box................................................. 202
Cupholder(s).............................................. 202
Front Storage Area.................................... 202
Center Console Storage Area.................... 202
Tonneau Cover......................................... 203
Sunroof....................................................... 205
Section 2 Features and Controls
114

Starting and Operating Your
Vehicle
New Vehicle Break-In
Notice:Your vehicle does not need an
elaborate break-in. But it will perform better in
the long run if you follow these guidelines:
Keep your speed at 55 mph (88 km/h)
or less for the rst 500 miles (805 km).
Do not drive at any one constant speed, fast
or slow, for the rst 500 miles (805 km). Do
not make full-throttle starts. Avoid
downshifting to brake, or slow, the vehicle.
Avoid making hard stops for the rst
200 miles (322 km) or so. During this time
your new brake linings are not yet broken
in. Hard stops with new linings can mean
premature wear and earlier replacement.
Follow this breaking-in guideline every time
you get new brake linings.
Do not tow a trailer during break-in. See
Towing a Trailer on page 429for the trailer
towing capabilities of your vehicle and more
information.
Following break-in, engine speed and load can
be gradually increased.
134

See “Range Selection Mode” later in this section.
PARK (P):This position locks your rear wheels. It
is the best position to use when you start your
engine because your vehicle cannot move easily. If
your vehicle has the Allison Transmission
®, with the
Power Take-Off (PTO), use PARK (P) when
starting. The Allison Transmission
®has a park pawl
that is designed to hold the weight of commercial
medium duty trucks. Therefore, the Allison
Transmission
®uses larger parts than other
automatic transmissions. These larger parts may
sometimes make a clunking noise when the
selector lever is moved from DRIVE (D) or
REVERSE (R) to PARK (P). This is normal and
there is no damage occurring during these shifts.
When parked on a hill, especially with a heavy load,you may notice an increase in the effort to shift out
of Park. See Torque Lock (Automatic Transmission)
underShifting Into Park (P) (Automatic
Transmission) on page 170for more information.
{CAUTION:
It is dangerous to get out of your vehicle
if the shift lever is not fully in PARK (P)
with the parking brake rmly set. Your
vehicle can roll.
Do not leave your 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 your vehicle will not
move, even when you are on fairly level
ground, always set your parking brake
and move the shift lever to PARK (P).
SeeShifting Into Park (P) (Automatic
Transmission) on page 170. If you are
pulling a trailer, seeTowing a Trailer on
page 429.
Allison Transmission®
141

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.
Downshifting the transmission in slippery road
conditions could result in skidding, see “Skidding”
underLoss of Control on page 371
DRIVE (D) can be used when towing a trailer,
carrying a heavy load, driving on steep hills, or for
off-road driving. You may want to shift the
transmission to THIRD (3) or, if necessary, a lower
gear selection if the transmission shifts too often.
If your vehicle has the Allison Transmission
®, it will
shift into rst range when DRIVE (D) is selected.
As vehicle speed increases, the transmission
will upshift automatically through each available
range up to SIXTH (6). As the vehicle slows,
the transmission will downshift automatically.The Allison Transmission
®uses 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 will be able
to maintain vehicle speed by analyzing things
such as throttle position, vehicle load, and
hill grade. If the shift stabilization feature
determines that current vehicle speed cannot be
maintained, the transmission does not upshift
and instead holds the current gear. In some cases,
this may appear to be a delayed shift, however
the transmission is operating normally.
The Allison Transmission
®also uses adaptive shift
controls. Adaptive shift controls continually
compares key shift parameters to pre-programmed
ideal shift conditions. The Allison Transmission
®
constantly makes adjustments to improve vehicle
performance according to the way the vehicle is
being used, such as with a heavy load. During this
adaptive shift controls process, some shifts may
feel different as the transmission determines
optimum settings for a particular shift.
143

MANUAL MODE (M):This position, is available
on vehicles with the Allison 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
®) later in this section.
THIRD (3):This position is also used for normal
driving. However, it reduces vehicle speed
more than DRIVE (D) without using your 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.
SECOND (2):This position reduces vehicle speed
even more than THIRD (3) without using your
brakes. You can use SECOND (2) on hills. It can
help control your speed as you go down steep
mountain roads, but then you would also want to
use your brakes off and on.
If you manually select SECOND (2) 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 your vehicle from a stop on
slippery road surfaces.For an Allison Transmission
®, see Low Traction
Mode later in this section.
FIRST (1):For an automatic transmission, this
position reduces vehicle speed even more than
SECOND (2) without using your brakes. You can
use it on very steep hills, or in deep snow or mud. If
the shift lever is put in FIRST (1) while the vehicle is
moving forward, the transmission will not shift into
rst gear until the vehicle is going slowly enough.
For an Allison Transmission
®, This position reduces
vehicle speed, without using your brakes. You can
use it for major/sever downgrades and off-road
driving where the vehicle would otherwise
accelerate due to steepness of grade. When you
shift to FIRST (1) it will provide the lowest gear
appropriate to your current road speed and will
continue to downshift as the vehicle slows,
eventually downshifting to FIRST (1) 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
your warranty. If you are stuck, do not spin
the tires. When stopping on a hill, use the
brakes to hold the vehicle in place.
144

Tow/Haul Mode
If your vehicle has an automatic transmission, it
may have a Tow/Haul mode. If your vehicle has an
Allison Transmission
®see “Tow/Haul Mode
(Allison Transmission®) following. 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 264for
more information.
If your vehicle has the Performance
Package-Enhanced Towing, activating the manual
selectable ride will adjust the shock absorber
characteristics to enhance the ride and handling of
the vehicle for towing or hauling heavy loads.
Also see Tow Haul Mode underTowing a Trailer
on page 429for more information.
147

Tow/Haul Mode (Allison
Transmission®)
If your vehicle has an Allison Transmission®,it
may have a Tow/Haul mode. 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 264for more
information.
Also see “Tow Haul Mode” underTowing a Trailer
on page 429for more information.
Grade Braking and Cruise Grade
Braking (Allison Transmission®)
Grade Braking and Cruise Grade Braking assists
when driving on a downhill grade. It maintains
the vehicle’s speed by automatically using a shift
schedule that uses the engine and the
transmission to slow the vehicle. This reduces
wear on the brakes system and increases control
of the vehicle. The system constantly monitors
the vehicle’s speed, acceleration, engine torque,
and brake pedal usage. It detects when the
truck is on a downhill grade and the driver’s desire
to slow down by pressing the brake.
148

Cruise Grade Braking is available on the 6.6L
DURAMAX®diesel engine. Cruise Grade Braking
monitors a vehicle’s cruise state, engine torque,
acceleration, vehicle speed, and the cruise set
speed. Using this information, it detects when the
truck is accelerating on a downhill grade and will
automatically downshift to slow the vehicle if it
exceeds the cruise set speed by a certain amount.
SeeCruise Control on page 217for more
information.
The Tow/Haul mode and Grade Braking shift
modes can be activated by pressing the button on
the end of the shift control stalk. If your vehicle
has the DURAMAX
®diesel Engine or the
8.1L VORTEC™ gasoline engine, Grade Braking
is only available while the Tow/Haul Mode is
selected. While in the Range Selection Mode,
Grade Braking is deactivated allowing the driver to
select a desired range of gears.
SeeAutomatic Transmission Operation on
page 140for more information.
Also seeTowing a Trailer on page 429for more
information.
Manual Transmission Operation
Five-Speed
(VORTEC™ 6.0L V8 Engine)
Here is how to operate
your transmission.
FIRST (1) is intended only for heavy loads or
trailer towing and is not recommended for normal
driving.
During the rst 500 miles (805 km) of vehicle use,
start your vehicle moving in FIRST (1). This
allows clutch components to break-in properly.
149