Hummer 2007 H2 Owner's Manual page 331

Q:
Suppose, after stalling, I try to back down
the hill and decide I just cannot do it.
What should I do?
A:
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.
331