2008 HUMMER H2 transmission

Crossing Obstacles
Approach Angle — a Key to Mobility
If you encounter a large dip in the terrain, do not
enter straight on; enter at an angle — 15° minimum
approach (A), 75° maximum approach angle (B).
For very large dips, ditches or small washes, coast in,
using the engine as a brake (transmission and
transfer case lowest gears). Then, use the low ranges
in the transmission and transfer case to power out.
Roll Your Tires Over Large Rocks
Do not straddle large
rocks; drive over them,
letting the tire cover
the rock. The tread of
the tire is thicker and
tougher than the sidewall
of the tire and is more
resilient to impact
than underbody
components.
4-21

Log Crossing
Using the proper technique, your vehicle will cross logs
up to 10 inches (25.4 cm) in diameter. Approach the log
at approximately a 15° angle (A) with the transmission in
FIRST (1) and the transfer case in 4LO LOCK and “walk”
your vehicle over, one tire at a time. It may be necessary
to modulate your brake pedal and accelerator to avoid
spin-out. Ease the vehicle down from the log with
your brake.
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.
4-22

Driving Uphill
Once you decide you can safely drive up the hill, you
need to take some special steps:
Use transmission and transfer case 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.
Let the traction system work to control any wheel
slippage. The traction control system allows for
moderate wheel spin with some capability to dig in
and power up the hill.
Do not continue if the vehicle shudders or exhibits
suspension hopping. This can cause damage to
the driveline or suspension components. Improper
driving technique is not covered by your vehicle
warranty.
{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.
4-24

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).
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.
4-25

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.
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.
{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 4 HI, 4 HI Lock, or 4 LO
Lock position.
4-26

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.
4-27

Hill and Mountain Roads
Driving on steep hills or through mountains is different
than driving on at or rolling terrain. Tips for driving
in these conditions include:
Keep your vehicle serviced and in good shape.
Check all uid levels and brakes, tires, cooling
system, and transmission.
Going down steep or long hills, shift to a
lower gear.
{CAUTION:
If you do not shift down, the brakes could get
so hot that they would not work well. You
would then have poor braking or even none
going down a hill. You could crash. Shift down
to let the engine assist the brakes on a steep
downhill slope.
{CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. The brakes will have
to do all the work of slowing down and they
could get so hot that they would not work well.
You would then have poor braking or even
none going down a hill. You could crash.
Always have the engine running and your
vehicle in gear when you go downhill.
Stay in your own lane. Do not swing wide or cut
across the center of the road. Drive at speeds
that let you stay in your own lane.
Top of hills: Be alert — something could be in your
lane (stalled car, accident).
Pay attention to special road signs (falling rocks
area, winding roads, long grades, passing or
no-passing zones) and take appropriate action.
SeeOff-Road Driving on page 4-13for information
about driving off-road.
4-35

Rocking Your Vehicle to Get It Out
First, turn the steering wheel left and right to clear
the area around the front wheels. The traction control
system activates when the system senses that the
wheels are spinning. SeeTraction Control System (TCS)
on page 4-5. Then, shift back and forth between
REVERSE (R) and a forward gear, spinning the wheels
as little as possible. To prevent transmission wear,
wait until the wheels stop spinning before shifting gears.
Release the accelerator pedal while you shift, and
press lightly on the accelerator pedal when the
transmission is in gear. By slowly spinning the wheels in
the forward and reverse directions, you will cause a
rocking motion that could free your vehicle. If that does
not get your vehicle out after a few tries, it might
need to be towed out. Or, you can use the recovery
loops. If your vehicle does need to be towed out,
seeTowing Your Vehicle on page 4-51.
Recovery Loops
{CAUTION:
These loops, when used, are under a lot of
force. Keep people away from the vicinity of
the loops and any chains or cables during use.
Always pull the vehicle straight out. Never pull
on the loops at a sideways angle. The loops
could break off and you or others could be
injured from the chain or cable snapping back.
Notice:Never use the recovery loops to tow the
vehicle. Your vehicle could be damaged and it would
not be covered by warranty.
4-40