2001 GMC YUKON Off road

4-26 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.

4-27
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.
CAUTION:
Driving across an incline that's too steep will
make your vehicle roll over. You could be
seriously injured or killed. If you have any doubt
about the steepness of the incline, don't drive
across it. Find another route instead.

4-29 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
-- 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. You may
want to reduce the air pressure in your tires slightly
when driving on sand. This will improve traction.
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
Light rain causes no special off-road driving problems.
But heavy rain can mean flash flooding, and flood
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
-- you probably won't get
through. Also, water that deep can damage your axle
and other vehicle parts.

4-30
If the water isn't too deep, then drive through it slowly.
At fast 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 ªDriving Through Waterº in the Index for more
information on driving through water.
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 fire 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.

4-31
Driving at Night
Night driving is more dangerous than day driving.
One reason is that some drivers are likely to be
impaired
-- by alcohol or drugs, with night vision
problems, or by fatigue.Here are some tips on night driving.

Drive defensively.

Don't drink and drive.

Adjust your inside rearview mirror to reduce the
glare from headlamps behind you.

Since you can't see as well, you may need to
slow down and keep more space between you and
other vehicles.

Slow down, especially on higher speed roads. Your
headlamps can light up only so much road ahead.

In remote areas, watch for animals.

If you're tired, pull off the road in a safe place
and rest.
No one can see as well at night as in the daytime. But as
we get older these differences increase. A 50
-year-old
driver may require at least twice as much light to see the
same thing at night as a 20
-year-old.
What you do in the daytime can also affect your night
vision. For example, if you spend the day in bright
sunshine you are wise to wear sunglasses. Your eyes
will have less trouble adjusting to night. But if you're
driving, don't wear sunglasses at night. They may cut
down on glare from headlamps, but they also make a
lot of things invisible.

4-38
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.
Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in flat or rolling terrain.

4-39
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 ªOff
-Road
Drivingº in the Index for information about
driving off
-road.

Keep your vehicle in good shape. Check all fluid
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.
CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. Your brakes will have to
do all the work of slowing down. They 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. Always have your engine running
and your vehicle in gear when you go downhill.

Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your engine
and transmission, and you can climb the hill better.

Stay in your own lane when driving on two
-lane
roads in hills or mountains. Don't swing wide or cut
across the center of the road. Drive at speeds that let
you stay in your own lane.

As you go over the top of a hill, be alert. There could be
something in your lane, like a stalled car or an accident.

You may see highway signs on mountains that warn of
special problems. Examples are long grades, passing or
no
-passing zones, a falling rocks area or winding
roads. Be alert to these and take appropriate action.

4-41
What's the worst time for this? ªWet ice.º Very cold
snow or ice can be slick and hard to drive on. But wet
ice can be even more trouble because it may offer the
least traction of all. You can get wet ice when it's about
freezing (32F; 0C) and freezing rain begins to fall.
Try to avoid driving on wet ice until salt and sand crews
can get there.
Whatever the condition
-- smooth ice, packed, blowing
or loose snow
-- drive with caution.Accelerate gently. Try not to break the fragile traction.
If you accelerate too fast, the drive wheels will spin and
polish the surface under the tires even more.
Your anti
-lock brakes improve your vehicle's stability
when you make a hard stop on a slippery road. Even
though you have an anti
-lock braking system, you'll
want to begin stopping sooner than you would on dry
pavement. See ªAnti
-Lockº in the Index.

Allow greater following distance on any
slippery road.

Watch for slippery spots. The road might be fine
until you hit a spot that's covered with ice. On an
otherwise clear road, ice patches may appear in
shaded areas where the sun can't reach: around
clumps of trees, behind buildings or under bridges.
Sometimes the surface of a curve or an overpass
may remain icy when the surrounding roads are
clear. If you see a patch of ice ahead of you,
brake before you are on it. Try not to brake
while you're actually on the ice, and avoid
sudden steering maneuvers.