GMC 2011 Sierra Denali Owner's Manual page 299

Low is to have the vehicle moving
1.6 to 3.2 km/h (1 to 2 mph). Turn the
knob to the Four-Wheel Drive Low
position. You must wait for the
Four-Wheel Drive Low indicator light
to stop flashing and remain on
before shifting the transmission
into gear.
Notice: Shifting the transmission
into gear before the requested
mode indicator light has stopped
flashing could damage the
transfer case. To help avoid
damaging the vehicle, always wait
for the mode indicator lights to
stop flashing before shifting the
transmission into gear.
It is typical for the vehicle to exhibit
significant engagement noise and
bump when shifting between
Four-Wheel Drive Low and
Four-Wheel Drive High ranges or
from transfer case N (Neutral) with
the engine running.
If the knob is turned to the
Four-Wheel Drive Low position
when the vehicle is in gear and/or
moving more than 1.6 to 3.2 km/h
(1 to 2 mph), the Four-Wheel Drive
Low indicator light will flash for
30 seconds and not complete the
shift. After 30 seconds the transfer
case will shift to Four-Wheel Drive
High mode. With the vehicle moving
less than 5 km/h (3 mph) and the
transmission in N (Neutral), attempt
the shift again.
Shifting Out of Four-Wheel
Drive Low
To shift from Four-Wheel Drive Low
to Four-Wheel Drive High or
Two-Wheel Drive High, the vehicle
must be stopped or moving less
than 5 km/h (3 mph) with the
transmission in N (Neutral) and
the ignition in ON/RUN. The
preferred method for shifting out of
Four-Wheel Drive Low is to have
the vehicle moving 1.6 to 3.2 km/h
Driving and Operating
(1 to 2 mph). Turn the knob to the
Four-Wheel Drive High or
Two-Wheel Drive High position.
You must wait for the Four-Wheel
Drive High or Two-Wheel Drive High
indicator light to stop flashing and
remain on before shifting the
transmission into gear.
Notice: Shifting the transmission
into gear before the requested
mode indicator light has stopped
flashing could damage the
transfer case. To help avoid
damaging the vehicle, always wait
for the mode indicator lights to
stop flashing before shifting the
transmission into gear.
It is typical for the vehicle to exhibit
significant engagement noise and
bump when shifting between
Four-Wheel Drive Low and
Four-Wheel Drive High ranges or
from transfer case N (Neutral) with
the engine running.
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