2010 GMC SIERRA DENALI Owners Manual

When driving over obstacles or rough terrain, keep a
firm grip on the steering wheel. Ruts, troughs, or other
surface features can jerk the wheel out of your hands.
When driving 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.
Off-roading requires a different kind of alertness from
driving on paved roads and highways. There are no
road signs, posted speed limits, or signal lights. Use
good judgment about what is safe and what is not.Driving on 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 the vehicle can and cannot
do. There are some hills that simply cannot be driven,
no matter how well built the vehicle.
{WARNING:
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.
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Approaching a Hill
When you approach a hill, decide if it is 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 might not see this because the
crest of the hill is hidden by bushes, grass, or shrubs.
Consider this 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 find 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 it is safe to drive up the hill:
.Use a low gear and get a firm grip on the steering
wheel.
.Get a smooth start up the hill and try to maintain
speed. Not using more power than needed can
avoid spinning the wheels or sliding.
{WARNING:
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 find
another route.
.Ease up on the speed as you approach the top of
the hill.
.Attach a flag to the vehicle to be more visible to
approaching traffic on trails or hills.
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.Sound the horn as you approach the top of the hill
to let opposing traffic know you are there.
.Use headlamps even during the day to make the
vehicle more visible to oncoming traffic.
{WARNING:
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.
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 and apply the parking
brake.
.If the engine is still running, shift the transmission
to R (Reverse), release the parking brake, and
slowly back down the hill in R (Reverse).
.If the engine has stopped running, you need to
restart it. With the brake pedal pressed and the
parking brake still applied, shift the transmission to
P (Park) and restart the engine. Then, shift to
R (Reverse), release the parking brake, and slowly
back down the hill as straight as possible in
R (Reverse).
.While backing down the hill, put your left hand on
the steering wheel at the 12 o'clock position so you
can tell if the wheels are straight and can
maneuver as you back down. It is best to 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.
Things not to do if the vehicle stalls, or is about to stall,
when going up a hill:
.Never attempt to prevent a stall by shifting into
N (Neutral) to rev-up the engine and regain forward
momentum. This will not work. The vehicle can roll
backward very quickly and could go out of control.
.Never try to turn around if about to stall when
going up a hill. If the hill is steep enough to stall
the vehicle, it is steep enough to cause it to roll
over. If you cannot make it up the hill, back straight
down the hill.
5-19

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 P (Park), 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.
Driving Downhill
When off-roading takes you downhill, consider:
.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, try to keep
the vehicle headed straight down. Use a low gear so
engine drag can help the brakes so they do not have to
do all the work. Descend slowly, keeping the vehicle
under control at all times.
{WARNING:
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.
Things not to do when driving down a hill:
.When driving downhill, avoid turns that take you
across the incline of the hill. A hill that is not too
steep to drive down might be too steep to drive
across. The vehicle could roll over.
.Never go downhill with the transmission in
N (Neutral), called free-wheeling. The brakes will
have to do all the work and could overheat
and fade.
Vehicles are much more likely to stall when going uphill,
but if it happens when going downhill: 1. Stop the vehicle by applying the regular brakes and apply the parking brake.
2. Shift to P (Park) and, while still braking, restart the engine.
5-20

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.
Driving Across an Incline
An off-road trail will probably go across the incline of a
hill. To decide whether to try to drive across the incline,
consider the following:
{WARNING:
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
might be too steep to drive across. When going
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 driving across
an incline, the narrower track width —the distance
between the left and right wheels —might not
prevent the vehicle from tilting and rolling over. Driving across an incline puts more weight on the
downhill wheels which could cause a downhill slide
or a rollover.
.Surface conditions can be a problem. Loose
gravel, muddy spots, or even wet grass can cause
the 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, the vehicle can tilt
even more.
For these reasons, carefully consider 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.
If you feel the vehicle starting to slide sideways, turn
downhill. This should help straighten out the vehicle and
prevent the side slipping. The best way to prevent this
is to “walk the course” first, so you know what the
surface is like before driving it.
5-21

Stalling on an Incline
{WARNING:
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 the vehicle stalls when 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.
Driving in Mud, Sand, Snow, or Ice
When you drive in mud, snow, or sand, the wheels do
not get good traction. Acceleration is not as quick,
turning is more difficult, and braking distances are
longer.
It is best to use a low gear when in mud —the deeper
the mud, the lower the gear. In really deep mud, keep
the vehicle moving so it does not get stuck. When driving on sand, wheel traction changes. On
loosely packed sand, such as on beaches or sand
dunes, the tires will tend to sink into the sand. This
affects 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 the vehicle does get
moving, poor steering and difficult braking can cause it
to slide out of control.
{WARNING:
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.
5-22

Driving in Water
{WARNING:
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it is
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Do not drive
through rushing water.
Heavy rain can mean flash flooding, and flood waters
demand extreme caution.
Find out how deep the water is before driving through it.
Do not try it if it is deep enough to cover the wheel
hubs, axles, or exhaust pipe —you probably will not get
through. Deep water can damage the axle and other
vehicle parts.
If the water is not too deep, drive slowly through it. At
faster speeds, water splashes on the ignition system
and the vehicle can stall. Stalling can also occur if you
get the tailpipe under water. If the tailpipe is under
water, you will never be able to start the engine. When
going through water, remember that when the brakes
get wet, it might take longer to stop. See Driving in Rain
and on Wet Roads on page 5‑24.
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 and check the fuel lines and cooling system
for any leakage.
The vehicle requires more frequent service due to
off-road use. Refer to the Maintenance Schedule for
additional information.
5-23

Driving at Night
Night driving is more dangerous than day driving
because some drivers are likely to be impaired—by
alcohol or drugs, with night vision problems, or by
fatigue.
Night driving tips include:
.Drive defensively.
.Do not drink and drive.
.Reduce headlamp glare by adjusting the inside
rearview mirror.
.Slow down and keep more space between you and
other vehicles because headlamps can only light
up so much road ahead.
.Watch for animals.
.When tired, pull off the road.
.Do not wear sunglasses.
.Avoid staring directly into approaching headlamps.
.Keep the windshield and all glass on your vehicle
clean —inside and out.
.Keep your eyes moving, especially during turns or
curves.
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 might need at least twice as much
light to see the same thing at night as a 20-year-old.
Driving in Rain and on Wet Roads
Rain and wet roads can reduce vehicle traction and
affect your ability to stop and accelerate. Always drive
slower in these types of driving conditions and avoid
driving through large puddles and deep‐standing or
flowing water.
{WARNING:
Wet brakes can cause crashes. They might not
work as well in a quick stop and could cause
pulling to one side. You could lose control of the
vehicle.
After driving through a large puddle of water or a
car/vehicle wash, lightly apply the brake pedal
until the brakes work normally.
Flowing or rushing water creates strong forces.
Driving through flowing water could cause your
vehicle to be carried away. If this happens, you
and other vehicle occupants could drown. Do not
ignore police warnings and be very cautious about
trying to drive through flowing water.
5-24