GMC Sierra 2008, Owner'S Manual, Page: 132 / 578

If the knob is turned to the Four-Wheel-Drive Low
position when your vehicle is in gear and/or moving,
the Four-Wheel-Drive 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-Drive High mode.
Shifting Out of Four-Wheel-Drive Low
To shift from Four-Wheel-Drive Low to Four-Wheel-Drive
High, or Two-Wheel-Drive 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
ON/RUN. The preferred method for shifting out of
Four-Wheel-Drive Low is to have your vehicle moving
1 to 2 mph (1.6 to 3.2 km/h). 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 your vehicle, always
wait for the mode indicator lights 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-Drive Low and Four-Wheel-Drive High
ranges or from NEUTRAL with the engine running.
If the knob is turned to the Four-Wheel-Drive High, or
Two-Wheel-Drive High switch position when your vehicle
is in gear and/or moving, the Four-Wheel-Drive High,
or Two-Wheel-Drive High indicator light will flash
for 30 seconds but will not complete the shift unless
your vehicle is moving less than 3 mph (5 km/h) and
the transmission is in NEUTRAL (N).
Shifting into NEUTRAL
To shift the transfer case to NEUTRAL do the following:
1. Make sure the vehicle is parked so that it will
not roll.
2. Set the parking brake and press and hold the
regular brake pedal. See Parking Brake on
page 2-48 for more information.
3. Start the vehicle or turn the ignition to ON/RUN.
4. Shift the transmission to NEUTRAL (N).
5. Shift the transfer case to Two-Wheel-Drive High.
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