wheel GMC ENVOY DENALI 2008 Service Manual

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.
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.
Adding non-dealer/non-retailer accessories can affect
your vehicle’s performance. SeeAccessories and
Modifications on page 5-3.
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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 4-3.
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
until the right front tire contacts the pavement edge. Then
turn the steering wheel to go straight down the roadway.
Passing
Passing another vehicle on a two-lane road can be
dangerous. To reduce the risk of danger while passing,
we suggest the following tips:
Look down the road, to the sides, and to crossroads
for situations that might affect a successful pass.
If in doubt, wait.
Watch for traffic signs, pavement markings, and
lines that could indicate a turn or an intersection.
Never cross a solid or double-solid line on your
side of the lane.
Do not get too close to the vehicle you want to
pass. Doing so can reduce your visibility.
Wait your turn to pass a slow vehicle.
When you are being passed, ease 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.
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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, the 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.
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 want to slow down and adjust your driving to these
conditions. It is important to slow down on slippery
surfaces because stopping distance is 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 might 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 Antilock 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 4-3. If your vehicle does
not have four-wheel drive, 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.
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“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.
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.
Loading Your Vehicle for Off-Road
Driving
{CAUTION:
Cargo on the load oor piled higher than
the seatbacks can be thrown forward during
a sudden stop. You or your passengers
could be injured. Keep cargo below the
top of the seatbacks.
Unsecured cargo on the load oor can be
tossed about when driving over rough
terrain. You or your passengers can be
struck by ying objects. Secure the cargo
properly.
Heavy loads on the roof raise the vehicle’s
center of gravity, making it more likely to
roll over. You can be seriously or fatally
injured if the vehicle rolls over. Put heavy
loads inside the cargo area, not on the roof.
Keep cargo in the cargo area as far forward
and low as possible.
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There are some important things to remember about
how to load your vehicle.
The heaviest things should be on the load oor and
forward of the rear axle. Put heavier items as far
forward as you can.
Be sure the load is secured properly, so driving on
the off-road terrain does not toss things around.
You will nd other important information in this manual.
SeeLoading Your Vehicle on page 4-34,Luggage
Carrier on page 2-58, andTires on page 5-57.
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.
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Getting Familiar with Off-Road Driving
It is a good idea to practice in an area that is safe
and close to home before you go into the wilderness.
Off-road driving does require some new and different
skills. Here is what we mean.
Tune your senses to different kinds of signals. Your
eyes, for example, need to constantly sweep the terrain
for unexpected obstacles. Your ears need to listen
for unusual tire or engine sounds. With your arms,
hands, feet, and body, you will need to respond to
vibrations and vehicle bounce.
Controlling your vehicle is the key to successful off-road
driving. One of the best ways to control your vehicle
is to control your speed. Here are some things to keep
in mind. At higher speeds:
You approach things faster and you have less time
to scan the terrain for obstacles.
You have less time to react.
You have more vehicle bounce when you drive over
obstacles.
You will need more distance for braking, especially
since you are on an unpaved surface.
{CAUTION:
When you are driving off-road, bouncing and
quick changes in direction can easily throw
you out of position. This could cause you to
lose control and crash. So, whether you are
driving on or off the road, you and your
passengers should wear safety belts.
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.
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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.
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.
SeeDrunk Driving on page 4-2.
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Driving Uphill
Once you decide you can safely drive up the hill, you
need to take some special steps.
Use a low gear and get a rm grip on the steering
wheel.
Get a smooth start up the hill and try to maintain
your speed. Do not use more power than you
need, because you do not want the wheels to
start spinning or sliding.
{CAUTION:
Turning or driving across steep hills can be
dangerous. You could lose traction, slide
sideways, and possibly roll over. You could
be seriously injured or killed. When driving up
hills, always try to go straight up.
Try to drive straight up the hill if at all possible.
If the path twists and turns, you might want to
nd another route.
Ease up on your speed as you approach the top of
the hill.
Attach a ag to the vehicle to make you more
visible to approaching traffic on trails or hills.
Sound the horn as you approach the top of the hill
to let opposing traffic know you are there.
Use your headlamps even during the day. They
make your vehicle more visible to oncoming traffic.
{CAUTION:
Driving to the top (crest) of a hill at full speed
can cause an accident. There could be a
drop-off, embankment, cliff, or even another
vehicle. You could be seriously injured or killed.
As you near the top of a hill, slow down and
stay alert.
There are some things you should do if the vehicle stalls,
or is about to stall, and you cannot make it up the hill:
Push the brake pedal to stop the vehicle and keep it
from rolling backwards. Also, apply the parking
brake.
If the engine is still running, shift the transmission to
REVERSE (R), release the parking brake, and slowly
back down the hill in REVERSE (R).
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If the engine has stopped running, you will need to
restart it. With the brake pedal pressed and the
parking brake still applied, shift the transmission
to PARK (P) and restart the engine. Then, shift to
REVERSE (R), release the parking brake, and
slowly back down the hill as straight as possible
in REVERSE (R).
As you are backing down the hill, put your left hand
on the steering wheel at the 12 o’clock position. This
way, you will be able to tell if the wheels are straight
and maneuver as you back down. It is best that you
back down the hill with the wheels straight rather
than in the left or right direction. Turning the wheel
too far to the left or right will increase the possibility
of a rollover.
There are also some things you must not do if you stall,
or are about to stall, when going up a hill:
Never attempt to prevent a stall by shifting into
NEUTRAL (N) to rev-up the engine and regain
forward momentum. This will not work. Your vehicle
will roll backwards very quickly and you could go
out of control.
Instead, apply the regular brake to stop the vehicle.
Then apply the parking brake. Shift to REVERSE (R),
release the parking brake, and slowly back
straight down.
Never attempt to turn around if you are about to stall
when going up a hill. If the hill is steep enough to stall
your vehicle, it is steep enough to cause you to roll
over if you turn around. If you cannot make it up the
hill, you must back straight down the hill.
If, after stalling, you try to back down the hill and decide
you just cannot do it, set the parking brake, put the
transmission in PARK (P) and turn off the engine. Leave
the vehicle and go get some help. Exit on the uphill side
and stay clear of the path the vehicle would take if it rolled
downhill. Do not shift the transfer case to NEUTRAL
when you leave the vehicle. Leave it in some gear.
{CAUTION:
Shifting the transfer case to NEUTRAL
can cause your vehicle to roll even if the
transmission is in PARK (P). This is because
the NEUTRAL position on the transfer case
overrides the transmission. You or someone
else could be injured. If you are going to leave
your vehicle, set the parking brake and shift
the transmission to PARK (P). But do not shift
the transfer case to NEUTRAL. Leave the
transfer case in the Two-Wheel High,
Four-Wheel High or Four-Wheel Low position.
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