2001 GMC YUKON XL DENALI Owners Manual

4-24 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.
Q:What if I'm driving across an incline that's not
too steep, but I hit some loose gravel and start to
slide downhill. What should I do?
A:If you feel your vehicle starting to slide sideways,
turn downhill. This should help straighten out the
vehicle and prevent the side slipping. However, a
much better way to prevent this is to get out and
ªwalk the courseº so you know what the surface is
like before you drive it.

4-25 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
-- 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.

4-26
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.
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.

4-27
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.
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.

4-28
Here are some tips on night driving.

Drive defensively.

Don't drink and drive.

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.You can be temporarily blinded by approaching
headlamps. It can take a second or two, or even several
seconds, for your eyes to readjust to the dark. When
you are faced with severe glare (as from a driver who
doesn't lower the high beams, or a vehicle with
misaimed headlamps), slow down a little. Avoid staring
directly into the approaching headlamps.
Keep your windshield and all the glass on your vehicle
clean
-- inside and out. Glare at night is made much
worse by dirt on the glass. Even the inside of the glass
can build up a film caused by dust. Dirty glass makes
lights dazzle and flash more than clean glass would,
making the pupils of your eyes contract repeatedly.
Remember that your headlamps light up far less of a
roadway when you are in a turn or curve. Keep your
eyes moving; that way, it's easier to pick out dimly
lighted objects. Just as your headlamps should be
checked regularly for proper aim, so should your eyes
be examined regularly. Some drivers suffer from night
blindness
-- the inability to see in dim light -- and
aren't even aware of it.

4-29
Driving in Rain and on Wet RoadsRain and wet roads can mean driving trouble. On a wet
road, you can't stop, accelerate or turn as well because
your tire
-to-road traction isn't as good as on dry roads.
And, if your tires don't have much tread left, you'll get
even less traction. It's always wise to go slower and be
cautious if rain starts to fall while you are driving. The
surface may get wet suddenly when your reflexes are
tuned for driving on dry pavement.
The heavier the rain, the harder it is to see. Even if your
windshield wiper blades are in good shape, a heavy rain
can make it harder to see road signs and traffic signals,
pavement markings, the edge of the road and even
people walking.
It's wise to keep your wiping equipment in good shape
and keep your windshield washer tank filled with
washer fluid. Replace your windshield wiper inserts
when they show signs of streaking or missing areas on
the windshield, or when strips of rubber start to separate
from the inserts.

4-30
Driving too fast through large water puddles or even
going through some car washes can cause problems, too.
The water may affect your brakes. Try to avoid puddles.
But if you can't, try to slow down before you hit them.
CAUTION:
Wet brakes can cause accidents. They won't work
as well in a quick stop and may cause pulling to
one side. You could lose control of the vehicle.
After driving through a large puddle of water or
a car wash, apply your brake pedal lightly until
your brakes work normally.
Hydroplaning
Hydroplaning is dangerous. So much water can build up
under your tires that they can actually ride on the water.
This can happen if the road is wet enough and you're
going fast enough. When your vehicle is hydroplaning,
it has little or no contact with the road.

4-31
Hydroplaning doesn't happen often. But it can if your
tires do not have much tread or if the pressure in one or
more is low. It can happen if a lot of water is standing on
the road. If you can see reflections from trees, telephone
poles or other vehicles, and raindrops ªdimpleº the
water's surface, there could be hydroplaning.
Hydroplaning usually happens at higher speeds. There
just isn't a hard and fast rule about hydroplaning. The
best advice is to slow down when it is raining.
Driving Through Deep Standing Water
NOTICE:
If you drive too quickly through deep puddles or
standing water, water can come in through your
engine's air intake and badly damage your
engine. Never drive through water that is slightly
lower than the underbody of your vehicle. If you
can't avoid deep puddles or standing water, drive
through them very slowly.
Driving Through Flowing Water
CAUTION:
Flowing or rushing water creates strong forces.
If you try to drive through flowing water, as you
might at a low water crossing, your vehicle can be
carried away. As little as six inches of flowing
water can carry away a smaller vehicle. If this
happens, you and the other vehicle occupants
could drown. Don't ignore police warning signs,
and otherwise be very cautious about trying to
drive through flowing water.
Some Other Rainy Weather Tips

Besides slowing down, allow some extra following
distance. And be especially careful when you pass
another vehicle. Allow yourself more clear room
ahead, and be prepared to have your view restricted
by road spray.

Have good tires with proper tread depth. See ªTiresº
in the Index.