wheel GMC SIERRA 2007 Repair Manual

Traction Control Operation
The traction control system is part of the
StabiliTrak®system. Traction control limits wheel
spin by reducing engine power to the wheels
(engine speed management) and by applying
brakes to each individual wheel (brake-traction
control) as necessary.
The traction control system is enabled
automatically when you start your vehicle. It will
activate and the StabiliTrak
®light will ash if
it senses that any of the wheels are spinning or
beginning to lose traction while driving. If you turn
off traction control, only the brake-traction
control portion of traction control will work. The
engine speed management will be disabled. In this
mode, engine power is not reduced automatically
and the driven wheels can spin more freely.
This can cause the brake-traction control to
activate constantly.Notice:If you allow the wheel(s) of one axle
to spin excessively while the StabiliTrak
®, ABS
and brake warning lights and the SERVICE
STABILITRAK message are displayed,
you could damage the transfer case. The
repairs would not be covered by your warranty.
Reduce engine power and do not spin the
wheel(s) excessively while these lights and this
message are displayed.
The traction control system may activate on dry or
rough roads or under conditions such as heavy
acceleration while turning or abrupt
upshifts/downshifts of the transmission. When this
happens, you may notice a reduction in
acceleration, or may hear a noise or vibration.
This is normal.
If your vehicle is in cruise control when the system
activates, the StabiliTrak
®light will ash and the
cruise control will automatically disengage.
When road conditions allow you to use cruise
again, you may re-engage the cruise control. See
Cruise Control on page 218.
StabiliTrak
®may also turn off automatically if it
determines that a problem exists with the system. If
the problem does not clear itself after restarting the
vehicle, you should see your dealer for service.
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Steering
Power Steering
If you lose power steering assist because the
engine stops or the system is not functioning, you
can steer but it will take much more effort.
Steering Tips
It is important to take curves at a reasonable
speed.
A lot of the “driver lost control” accidents mentioned
on the news happen on curves. Here is why:
Experienced driver or beginner, each of us is
subject to the same laws of physics when driving on
curves. The traction of the tires against the road
surface makes it possible for the vehicle to change
its path when you turn the front wheels. If there is
no traction, inertia will keep the vehicle going in the
same direction. If you have ever tried to steer a
vehicle on wet ice, you will understand this.
The traction you can get in a curve depends on
the condition of the tires and the road surface, the
angle at which the curve is banked, and your
speed. While you are in a curve, speed is the one
factor you can control.Suppose you are steering through a sharp curve.
Then you suddenly accelerate. Both control
systems — steering and acceleration — have to
do their work where the tires meet the road.
Adding the sudden acceleration can demand too
much of those places. You can lose control.
SeeStabiliTrak
®System on page 381.
What should you do if this ever happens? Ease up
on the accelerator pedal, steer the vehicle the
way you want it to go, and slow down.
Speed limit signs near curves warn that you
should adjust your speed. Of course, the posted
speeds are based on good weather and road
conditions. Under less favorable conditions you will
want to go slower.
If you need to reduce your speed as you approach
a curve, do it before you enter the curve, while
the front wheels are straight ahead.
Try to adjust your speed so you can “drive”
through the curve. Maintain a reasonable, steady
speed. Wait to accelerate until you are out of
the curve, and then accelerate gently into
the straightaway.
385

Adding non-GM accessories can affect your
vehicle’s performance. SeeAccessories and
Modications on page 486.
Steering in Emergencies
There are times when steering can be more
effective than braking. For example, you come
over a hill and nd a truck stopped in your lane, or
a car suddenly pulls out from nowhere, or a
child darts out from between parked cars and
stops right in front of you. You can avoid these
problems by braking — if you can stop in time. But
sometimes you cannot; there is not room. That
is the time for evasive action — steering around
the problem.
Your vehicle can perform very well in emergencies
like these. First, apply the brakes. SeeBraking
on page 378. It is better to remove as much speed
as you can from a possible collision. Then steer
around the problem, to the left or right depending
on the space available.An emergency like this requires close attention
and a quick decision. If you are holding the
steering wheel at the recommended 9 and
3 o’clock positions, you can turn it a full
180 degrees very quickly without removing either
hand. But you have to act fast, steer quickly,
and just as quickly straighten the wheel once you
have avoided the object.
The fact that such emergency situations are
always possible is a good reason to practice
defensive driving at all times and wear safety belts
properly.
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Off-Road Recovery
You may nd that your right wheels have dropped
off the edge of a road onto the shoulder while
you are driving.
If the level of the shoulder is only slightly below
the pavement, recovery should be fairly easy.
Ease off the accelerator and then, if there
is nothing in the way, steer so that your vehicle
straddles the edge of the pavement. You can turn
the steering wheel up to one-quarter turn untilthe right front tire contacts the pavement edge.
Then turn the steering wheel to go straight down
the roadway.
Passing
The driver of a vehicle about to pass another on a
two-lane highway waits for just the right moment,
accelerates, moves around the vehicle ahead, then
goes back into the right lane again. A simple
maneuver?
Not necessarily! Passing another vehicle on a
two-lane highway is a potentially dangerous move,
since the passing vehicle occupies the same
lane as oncoming traffic for several seconds. A
miscalculation, an error in judgment, or a
brief surrender to frustration or anger can suddenly
put the passing driver face to face with the
worst of all traffic accidents — the head-on
collision.
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Try not to pass more than one vehicle at a time
on two-lane roads. Reconsider before passing
the next vehicle.
Do not overtake a slowly moving vehicle
too rapidly. Even though the brake lamps are
not ashing, it may be slowing down or starting
to turn.
If you are being passed, make it easy for the
following driver to get ahead of you. Perhaps
you can ease a little to the right.
Loss of Control
Let us review what driving experts say
about what happens when the three
control systems — brakes, steering, and
acceleration — do not have enough friction
where the tires meet the road to do what the
driver has asked.
In any emergency, do not give up. Keep trying to
steer and constantly seek an escape route or
area of less danger.
Skidding
In a skid, a driver can lose control of the vehicle.
Defensive drivers avoid most skids by taking
reasonable care suited to existing conditions, and
by not overdriving those conditions. But skids
are always possible.
The three types of skids correspond to your
vehicle’s three control systems. In the braking skid,
your wheels are not rolling. In the steering or
cornering skid, too much speed or steering in a
curve causes tires to slip and lose cornering force.
And in the acceleration skid, too much throttle
causes the driving wheels to spin.
A cornering skid is best handled by easing your
foot off the accelerator pedal.
Remember: StabiliTrak
®helps avoid only the
acceleration skid. SeeStabiliTrak®System
on page 381. If the StabiliTrak®System is off,
then an acceleration skid is also best handled by
easing your foot off the accelerator pedal.
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If your vehicle starts to slide, ease your foot off
the accelerator pedal and quickly steer the
way you want the vehicle to go. If you start
steering quickly enough, your vehicle may
straighten out. Always be ready for a second skid
if it occurs.
Of course, traction is reduced when water, snow,
ice, gravel, or other material is on the road.
For safety, you will want to slow down and adjust
your driving to these conditions. It is important
to slow down on slippery surfaces because
stopping distance will be longer and vehicle control
more limited.
While driving on a surface with reduced traction, try
your best to avoid sudden steering, acceleration, or
braking, including reducing vehicle speed by
shifting to a lower gear. Any sudden changes could
cause the tires to slide. You may not realize the
surface is slippery until your vehicle is skidding.
Learn to recognize warning clues — such as
enough water, ice, or packed snow on the road to
make a mirrored surface — and slow down when
you have any doubt.
Remember: Any Anti-Lock Brake System (ABS)
helps avoid only the braking skid.Off-Road Driving
This off-road guide is for vehicles that have
four-wheel drive. Also, seeBraking on page 378.If
your vehicle does not have four-wheel drive or
is equipped with 20-inch tire/wheel assemblies,
you should not drive off-road unless you are on a
level, solid surface.
The airbag system is designed to work properly
under a wide range of conditions, including off-road
usage. Observe safe driving speeds, especially
on rough terrain. As always, wear your safety belt.
Off-road driving can be great fun. But it does
have some denite hazards. The greatest of these
is the terrain itself.
“Off-roading” means you have left the great North
American road system behind. Traffic lanes
are not marked. Curves are not banked. There are
no road signs. Surfaces can be slippery, rough,
uphill, or downhill. In short, you have gone
right back to nature.
Off-road driving involves some new skills. And that
is why it is very important that you read this
guide. You will nd many driving tips and
suggestions. These will help make your off-road
driving safer and more enjoyable.
390

If you think you will need some more ground
clearance at the front of your vehicle, you
can remove the front fascia lower air dam.
The front fascia lower air dam is held in place by
two bolts and 10 snap features. The bolts and
snap features are accessible from underneath the
front fascia.
The following steps must be performed on the
bolts and snap features to remove the air dam:
1. Remove the two outboard air dam bolts.
2. With a at-blade screwdriver, push down on
the snap features and disengage the snaps.
3. After the bolts are removed and the snaps are
disengaged, push forward on the air dam until
it is free.
When you are back on roads, though, be sure to
replace the air dam.
Notice:Operating your vehicle for extended
periods without the front fascia lower air
dam installed can cause improper air ow to
the engine. Always be sure to replace the front
fascia air dam when you are nished off-road
driving.To reinstall the lower air dam do the following:
1. Line up the snap features and push the
air dam rearward to engage the snaps.
2. Install the two outboard bolts.
Before You Go Off-Roading
There are some things to do before you go out.
For example, be sure to have all necessary
maintenance and service work done. Check to
make sure all underbody shields, if the vehicle has
them, are properly attached. Be sure you read
all the information about your four-wheel-drive
vehicle in this manual. Is there enough fuel? Is the
spare tire fully inated? Are the uid levels up
where they should be? What are the local
laws that apply to off-roading where you will be
driving? If you do not know, you should check with
law enforcement people in the area. Will you be
on someone’s private land? If so, be sure to
get the necessary permission.
391

Environmental Concerns
Off-road driving can provide wholesome and
satisfying recreation. However, it also raises
environmental concerns. We recognize these
concerns and urge every off-roader to follow these
basic rules for protecting the environment:
Always use established trails, roads, and areas
that have been specially set aside for public
off-road recreational driving; obey all
posted regulations.
Avoid any driving practice that could damage
the environment — shrubs, owers, trees,
grasses — or disturb wildlife. This includes
wheel-spinning, breaking down trees, or
unnecessary driving through streams or over
soft ground.
Always carry a litter bag — make sure all
refuse is removed from any campsite
before leaving.
Take extreme care with open res where
permitted, camp stoves, and lanterns.
Never park your vehicle over dry grass or
other combustible materials that could
catch re from the heat of the vehicle’s
exhaust system.
Traveling to Remote Areas
It makes sense to plan your trip, especially when
going to a remote area. Know the terrain and plan
your route. You are much less likely to get bad
surprises. Get accurate maps of trails and terrain.
Try to learn of any blocked or closed roads.
It is also a good idea to travel with at least one
other vehicle. If something happens to one
of them, the other can help quickly.
Does your vehicle have a winch? If so, be sure to
read the winch instructions. In a remote area, a
winch can be handy if you get stuck. But you will
want to know how to use it properly.
393

Scanning the Terrain
Off-road driving can take you over many different
kinds of terrain. You need to be familiar with
the terrain and its many different features. Here
are some things to consider.
Surface Conditions:Off-roading can take you
over hard-packed dirt, gravel, rocks, grass, sand,
mud, snow, or ice. Each of these surfaces
affects the steering, acceleration, and braking of
your vehicle in different ways. Depending upon the
kind of surface you are on, you may experience
slipping, sliding, wheel spinning, delayed
acceleration, poor traction, and longer braking
distances.Surface Obstacles:Unseen or hidden obstacles
can be hazardous. A rock, log, hole, rut, or
bump can startle you if you are not prepared for
them. Often these obstacles are hidden by
grass, bushes, snow, or even the rise and fall of
the terrain itself. Here are some things to consider:
Is the path ahead clear?
Will the surface texture change abruptly up
ahead?
Does the travel take you uphill or downhill?
There is more discussion of these subjects
later.
Will you have to stop suddenly or change
direction quickly?
When you drive over obstacles or rough terrain,
keep a rm grip on the steering wheel. Ruts,
troughs, or other surface features can jerk
the wheel out of your hands if you are not
prepared.
395

When you drive over bumps, rocks, or other
obstacles, the wheels can leave the ground. If this
happens, even with one or two wheels, you
cannot control the vehicle as well or at all.
Because you will be on an unpaved surface, it is
especially important to avoid sudden acceleration,
sudden turns, or sudden braking.
In a way, off-road driving requires a different kind of
alertness from driving on paved roads and
highways. There are no road signs, posted speed
limits, or signal lights. You have to use your own
good judgment about what is safe and what is not.
Drinking and driving can be very dangerous on
any road. And this is certainly true for off-road
driving. At the very time you need special alertness
and driving skills, your reexes, perceptions,
and judgment can be affected by even a small
amount of alcohol. You could have a serious — or
even fatal — accident if you drink and drive or
ride with a driver who has been drinking.
SeeDrunken Driving on page 375.Driving on Off-Road Hills
Off-road driving often takes you up, down, or
across a hill. Driving safely on hills requires good
judgment and an understanding of what your
vehicle can and cannot do. There are some hills
that simply cannot be driven, no matter how
well built the vehicle.
{CAUTION:
Many hills are simply too steep for any
vehicle. If you drive up them, you will
stall. If you drive down them, you cannot
control your speed. If you drive across
them, you will roll over. You could be
seriously injured or killed. If you have any
doubt about the steepness, do not drive
the hill.
396