2008 GMC YUKON Owner's Manual

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.
4-17

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.
Approaching a Hill
When you approach a hill, you need to decide if it is
one of those hills that is 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
will not have to make turning maneuvers?
Are there obstructions on the hill that can block your
path, such as boulders, trees, logs, or ruts?
What is beyond the hill? Is there a cliff, an
embankment, a drop-off, a fence? Get out and
walk the hill if you do not know. It is 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.
4-18

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 your engine is still running, shift the transmission to
REVERSE (R), release the parking brake, and slowly
back down the hill in REVERSE (R).
4-19

If your 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 your wheels are straight
and maneuver as you back down. It is 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.
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.
{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.
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 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.
4-20

Driving Downhill
When off-roading takes you downhill, you will want to
consider a number of things:
How steep is the downhill? Will I be able to maintain
vehicle control?
What is the surface like? Smooth? Rough? Slippery?
Hard-packed dirt? Gravel?
Are there hidden surface obstacles? Ruts? Logs?
Boulders?
What is 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 will not 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.There some things not to do when driving down a hill.
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 is not too
steep to drive down may be too steep to drive
across. You could roll over if you do not drive
straight down.
Never go downhill with the transmission in
NEUTRAL (N). This is called “free-wheeling.” Your
brakes will have to do all the work and could
overheat and fade.
Your vehicle is much more likely to stall when going
uphill. But if it happens when going downhill:
1. Stop your vehicle by applying the regular brakes.
Apply the parking brake.
2. Shift to PARK (P) and, while still braking, restart the
engine.
3. Shift back to a low gear, release the parking brake,
and drive straight down.
4. If the engine will not start, get out and get help.
4-21

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:
{CAUTION:
Driving across an incline that is 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, do
not drive across it. Find another route instead.
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 does not mean you have to
drive it. The last vehicle to try it might have rolled over.
When driving across an incline that is not too steep, the
vehicle can hit some loose gravel and start to slide
downhill. 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 “walk
the course” so you know what the surface is like
before you drive it.
4-22

Stalling on an Incline
{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.
If your vehicle stalls when you are crossing an incline,
be sure you, and any 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 will 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.
4-23

Driving in Mud, Sand, Snow, or Ice
When you drive in mud, snow, or sand, your wheels will
not get good traction. You cannot accelerate as
quickly, turning is more difficult, and you will need longer
braking distances.
It is best to use a low gear when you are in mud — the
deeper the mud, the lower the gear. In really deep
mud, the idea is to keep your vehicle moving so you do
not get stuck.
When you drive on sand, you will sense a change in
wheel traction. But it will depend upon how loosely
packed the sand is. On loosely packed sand, such 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.Hard packed snow and ice offer the worst tire traction.
On these surfaces, it is 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.
4-24