Chevrolet 2006 Avalanche Owner's Manual page 110

Shifting Into Four-Wheel Low
To shift to the Four-Wheel Low position, the ignition
must be in RUN and the vehicle must be stopped
or moving less than 3 mph (5 km/h) with the
transmission in NEUTRAL (N). The preferred method for
shifting into four-wheel low is to have your vehicle
moving 1 to 2 mph (1.6 to 3.2 km/h). Press and release
the Four-Wheel Low button. You must wait for the
four-wheel low indicator light to stop flashing and remain
on before shifting your transmission in gear.
Notice: Shifting the transmission into gear before
the Four-Wheel Low indicator light has stopped
flashing could damage the transfer case. To
help avoid damaging your vehicle, always wait for
the Four-Wheel Low indicator light to stop flashing
before shifting the transmission into gear.
It is typical for your vehicle to exhibit significant
engagement noise and bump when shifting between
Four-Wheel Low and Four-Wheel High ranges or from
NEUTRAL with the engine running.
If the Four-Wheel Low button is pressed when your
vehicle is in gear and/or moving, the Four-Wheel Low
indicator light will flash for 30 seconds and not complete
the shift unless your vehicle is moving less than
3 mph (5 km/h) and the transmission is in NEUTRAL (N).
After 30 seconds the transfer case will shift to
Four-Wheel High mode.
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Shifting Out of Four-Wheel Low
To shift from Four-Wheel Low to Four-Wheel High, AUTO
4WD or Two-Wheel High, your vehicle must be stopped
or moving less than 3 mph (5 km/h) with the transmission
in NEUTRAL (N) and the ignition in RUN. The preferred
method for shifting out of Four-Wheel Low is to have your
vehicle moving 1 to 2 mph (1.6 to 3.2 km/h). Press and
release the Four-Wheel High, AUTO 4WD or Two-Wheel
High button. You must wait for the Four-Wheel High,
AUTO 4WD or Two-Wheel High indicator light to stop
flashing and remain on before shifting your transmission
into gear.
Notice: Shifting the transmission into gear before
the Four-Wheel Low indicator light has stopped
flashing could damage the transfer case. To
help avoid damaging your vehicle, always wait for
the Four-Wheel Low indicator light to stop flashing
before shifting the transmission into gear.
It is typical for your vehicle to exhibit significant
engagement noise and bump when shifting between
Four-Wheel Low and Four-Wheel High ranges or from
NEUTRAL with the engine running.