wheel GMC ENVOY 2003 Service Manual

Approaching a Hill
When you approach a hill, you need to decide if it's one
of those hills that's just too steep to climb, descend
or cross. Steepness can be hard to judge. On a very
small hill, for example, there may be a smooth, constant
incline with only a small change in elevation where
you can easily see all the way to the top. On a large hill,
the incline may get steeper as you near the top, but
you may not see this because the crest of the hill
is hidden by bushes, grass or shrubs.
Here are some other things to consider as you approach
a hill.
·Is there a constant incline, or does the hill get
sharply steeper in places?
·Is there good traction on the hillside, or will the
surface cause tire slipping?
·Is there a straight path up or down the hill so you
won't have to make turning maneuvers?
·Are there obstructions on the hill that can block
your path (boulders, trees, logs or ruts)?
·What's beyond the hill? Is there a cliff, an
embankment, a drop-off, a fence? Get out and walk
the hill if you don't know. It's the smart way to
®nd out.
·Is the hill simply too rough? Steep hills often have
ruts, gullies, troughs and exposed rocks because
they are more susceptible to the effects of erosion.
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. Don't use more power than you
need, because you don't want your wheels to start
spinning or sliding.
·Try to drive straight up the hill if at all possible. If
the path twists and turns, you might want to ®nd
another route.
{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.
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·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're there.
·Use your headlamps even during the day. They
make you 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.
Q:What should I do if my vehicle stalls, or is
about to stall, and I can't make it up the hill?
A:If this happens, there are some things you should
do, and there are some things you must not do.
First, here's what you
shoulddo:
·Push the brake pedal to stop the vehicle and
keep it from rolling backwards. Also, apply the
parking brake.
·If your engine is still running, shift the transmission
to REVERSE (R), release the parking brake, and
slowly back down the hill in REVERSE (R).
·If your engine has stopped running, you'll 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'll be able to tell if your wheels
are straight and maneuver as you back down. It's
best that you back down the hill with your
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.
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Here are some things youmust notdo 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 ªrev-upº the engine and regain
forward momentum. This won't 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's steep enough to
cause you to roll over if you turn around. If you can't
make it up the hill, you must back straight down
the hill.
Q:Suppose, after stalling, I try to back down the
hill and decide I just can't do it. What should
I do?
A:Set the parking brake, put your 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 2 Wheel High, 4 High or
4 Low position.
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Driving Downhill
When off-roading takes you downhill, you'll want to
consider a number of things:
·How steep is the downhill? Will I be able to maintain
vehicle control?
·What's the surface like? Smooth? Rough? Slippery?
Hard-packed dirt? Gravel?
·Are there hidden surface obstacles? Ruts? Logs?
Boulders?
·What's at the bottom of the hill? Is there a hidden
creek bank or even a river bottom with large
rocks?
If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a
low gear. This way, engine drag can help your brakes
and they won't have to do all the work. Descend slowly,
keeping your vehicle under control at all times.
{CAUTION:
Heavy braking when going down a hill can
cause your brakes to overheat and fade. This
could cause loss of control and a serious
accident. Apply the brakes lightly when
descending a hill and use a low gear to keep
vehicle speed under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you ignore
them you could lose control and have a serious
accident.
·When driving downhill, avoid turns that take you
across the incline of the hill. A hill that's not too
steep to drive down may be too steep to drive
across. You could roll over if you don't drive straight
down.
·Never go downhill with the transmission in
NEUTRAL (N). This is called ªfree-wheeling.º Your
brakes will have to do all the work and could
overheat and fade.
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Q:Am I likely to stall when going downhill?
A:It's much more likely to happen going uphill. But if
it happens going downhill, here's what to do.
·Stop your vehicle by applying the regular brakes.
Apply the parking brake.
·Shift to PARK (P) and, while still braking, restart the
engine.
·Shift back to a low gear, release the parking brake,
and drive straight down.
·If the engine won't start, get out and get help.
Driving Across an Incline
Sooner or later, an off-road trail will probably go across
the incline of a hill. If this happens, you have to
decide whether to try to drive across the incline. Here
are some things to consider:
·A hill that can be driven straight up or down may be
too steep to drive across. When you go straight up
or down a hill, the length of the wheel base (the
distance from the front wheels to the rear wheels)
reduces the likelihood the vehicle will tumble
end over end. But when you drive across an incline,the much more narrow track width (the distance
between the left and right wheels) may not prevent
the vehicle from tilting and rolling over. Also,
driving across an incline puts more weight on the
downhill wheels. This could cause a downhill
slide or a rollover.
·Surface conditions can be a problem when you
drive across a hill. Loose gravel, muddy spots,
or even wet grass can cause your tires to slip
sideways, downhill. If the vehicle slips sideways, it
can hit something that will trip it (a rock, a rut,
etc.) and roll over.
·Hidden obstacles can make the steepness of the
incline even worse. If you drive across a rock
with the uphill wheels, or if the downhill wheels drop
into a rut or depression, your vehicle can tilt even
more.
For reasons like these, you need to decide carefully
whether to try to drive across an incline. Just because
the trail goes across the incline doesn't mean you
have to drive it. The last vehicle to try it might have
rolled over.
4-24

Stalling on an Incline
If your vehicle stalls when you're crossing an incline, be
sure you (and your passengers) get out on the uphill
side, even if the door there is harder to open. If you get
out on the downhill side and the vehicle starts to roll
over, you'll be right in its path.
If you have to walk down the slope, stay out of the path
the vehicle will take if it does roll over.{CAUTION:
Getting out on the downhill (low) side of a
vehicle stopped across an incline is
dangerous. If the vehicle rolls over, you could
be crushed or killed. Always get out on the
uphill (high) side of the vehicle and stay well
clear of the rollover path.
Driving in Mud, Sand, Snow or Ice
When you drive in mud, snow or sand, your wheels won't
get good traction. You can't accelerate as quickly, turning
is more difficult, and you'll need longer braking distances.
It's best to use a low gear when you're in mud Ð the
deeper the mud, the lower the gear. In really deep mud,
the idea is to keep your vehicle moving so you don't
get stuck.
When you drive on sand, you'll sense a change in
wheel traction. But it will depend upon how loosely
packed the sand is. On loosely packed sand (as
on beaches or sand dunes) your tires will tend to sink
into the sand. This has an effect on steering,
accelerating and braking. Drive at a reduced speed and
avoid sharp turns or abrupt maneuvers.
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Hard packed snow and ice offer the worst tire traction.
On these surfaces, it's very easy to lose control. On
wet ice, for example, the traction is so poor that you will
have difficulty accelerating. And if you do get moving,
poor steering and difficult braking can cause you to slide
out of control.
{CAUTION:
Driving on frozen lakes, ponds or rivers can be
dangerous. Underwater springs, currents
under the ice, or sudden thaws can weaken the
ice. Your vehicle could fall through the ice and
you and your passengers could drown. Drive
your vehicle on safe surfaces only.
Driving in Water
Heavy rain can mean ¯ash ¯ooding, and ¯ood waters
demand extreme caution.
Find out how deep the water is before you drive through
it. If it's deep enough to cover your wheel hubs, axles
or exhaust pipe, don't try it Ð you probably won't
get through. Also, water that deep can damage your
axle and other vehicle parts.If the water isn't too deep, drive slowly through it. At
faster speeds, water splashes on your ignition system
and your vehicle can stall. Stalling can also occur if you
get your tailpipe under water. And, as long as your
tailpipe is under water, you'll never be able to start your
engine. When you go through water, remember that
when your brakes get wet, it may take you longer
to stop.
{CAUTION:
Driving through rushing water can be
dangerous. Deep water can sweep your vehicle
downstream and you and your passengers
could drown. If it's only shallow water, it can
still wash away the ground from under your
tires, and you could lose traction and roll the
vehicle over. Don't drive through rushing water.
See
Driving in Rain and on Wet Roads on page 4-30for
more information on driving through water.
4-27

After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a ®re hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust
system for damage. Also, check the fuel lines and
cooling system for any leakage.
Your vehicle will require more frequent service due to
off-road use. Refer to the Maintenance Schedule
for additional information.
Driving at Night
Night driving is more dangerous than day driving.
One reason is that some drivers are likely to be
impaired Ð by alcohol or drugs, with night vision
problems, or by fatigue.
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Highway Hypnosis
Is there actually such a condition as ªhighway
hypnosisº? Or is it just plain falling asleep at the wheel?
Call it highway hypnosis, lack of awareness, or
whatever.
There is something about an easy stretch of road with
the same scenery, along with the hum of the tires on the
road, the drone of the engine, and the rush of the
wind against the vehicle that can make you sleepy. Don't
let it happen to you! If it does, your vehicle can leave
the road in
less than a second,and you could crash and
be injured.What can you do about highway hypnosis? First, be
aware that it can happen.
Then here are some tips:
·Make sure your vehicle is well ventilated, with a
comfortably cool interior.
·Keep your eyes moving. Scan the road ahead and
to the sides. Check your mirrors and your
instruments frequently.
·If you get sleepy, pull off the road into a rest,
service or parking area and take a nap, get some
exercise, or both. For safety, treat drowsiness
on the highway as an emergency.
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Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in ¯at or rolling terrain.
If you drive regularly in steep country, or if you're
planning to visit there, here are some tips that can make
your trips safer and more enjoyable.See
Off-Road Driving with Your Four-Wheel-Drive
Vehicle on page 4-15for information about driving
off-road.
·Keep your vehicle in good shape. Check all ¯uid
levels and also the brakes, tires, cooling system
and transmission. These parts can work hard
on mountain roads.
·Know how to go down hills. The most important
thing to know is this: let your engine do some of
the slowing down. Shift to a lower gear when you go
down a steep or long hill.
{CAUTION:
If you don't shift down, your brakes could get
so hot that they wouldn't work well. You would
then have poor braking or even none going
down a hill. You could crash. Shift down to let
your engine assist your brakes on a steep
downhill slope.
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