GMC Hummer H3 2008 Owner's Handbook Manual page 198

2 (Second Gear)
This position gives you even more
power than 3. You can use it on
steep hills.
This position reduces vehicle
speed even more than 3 (Third)
without using the brakes.
1 (First Gear)
This position gives you even more
power than 2. You can use it on
very steep hills or in deep snow or
mud.
This position reduces vehicle
speed even more than 2 (Second)
without using the brakes.
The transmission will not shift into
first gear until the vehicle is going
slowly enough.
Section 3
SHIFT LOCK CONTROL SYSTEM
Your vehicle has an automatic
transmission shift lock control
system. With the engine running,
you have to fully apply the regular
brakes and press the shift lever
button before you can shift out of
P (Park).
See "Vehicle Parking" later in this
section for more information.
197 . . .