Hummer 2004 H2 - Manual (Page 107)

Shifting into 4HI or 4HI Lock
With the vehicle traveling less than 40 mph (64 km/h),
press and release the 4HI or 4HI Lock button. The
indicator light will flash while shifting. It will remain
illuminated when the shift is complete.
It may be necessary to drive backwards for a short
distance of 25 feet (7.5 m) to get the lock feature
to disengage.
Shifting into 4LO Lock
To shift into 4LO Lock, the ignition must be in RUN and
the vehicle must be stopped or moving less than
2 mph (3.2 km/h) with the transmission in NEUTRAL (N).
The preferred method for shifting into 4LO is to have
your vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press
and release the 4LO Lock button. You must wait for
the 4LO Lock indicator light to stop flashing and remain
illuminated before shifting your transmission in gear.
Notice: Shifting the transmission into gear before
the indicator light stops flashing could cause
damage to the transfer case. Always wait until the
indicator lights stops flashing before putting
the transmission back in gear.
It is typical for your vehicle to exhibit significant
engagement noise and bump when shifting between
4LO and 4HI ranges or from NEUTRAL with the engine
running.
If the 4LO Lock button is pressed when your vehicle is
in gear and/or moving, the 4LO Lock indicator light
will flash for 15 seconds and not complete the
shift unless your vehicle is moving less than 2 mph
(3.2 km/h) and the transmission is in NEUTRAL (N).
After 15 seconds the transfer case will return to
the setting last chosen.
Shifting Out of 4LO Lock
To shift from 4LO Lock to 4HI or 4HI Lock, your vehicle
must be stopped or moving less than 2 mph (3.2 km/h)
with the transmission in NEUTRAL (N) and the ignition in
RUN. The preferred method for shifting out of 4LO
Lock is to have your vehicle moving 1 to 2 mph
(1.6 to 3.2 km/h). Press and release the 4HI or 4HI Lock
button. You must wait for the 4HI or 4HI Lock indicator
light to stop flashing and remain illuminated before
shifting your transmission into gear.
It is typical for your vehicle to exhibit significant
engagement noise and bump when shifting between
4LO and 4HI ranges or from NEUTRAL with the engine
running.
2-27