Hummer H2 2010 Owner's Manual page 341

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.
If, after stalling, you try to back down the hill and decide
you just cannot do it, set the parking brake, shift to
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.
Do not shift the transfer case to N (Neutral) when you
leave the vehicle. Leave it in some gear.
WARNING:
Shifting the transfer case to N (Neutral) can cause
your vehicle to roll even if the transmission is in
P (Park). This is because the N (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 P (Park). But do not
shift the transfer case to N (Neutral). Leave the
transfer case in the 4 HI, 4 HI Lock, or 4 LO Lock
position.
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