GMC 2006 Sierra - Manual (Page 144)

Shifting from Four-Wheel Low to
Four-Wheel High or Two-Wheel High
To shift from four-wheel low to Four-Wheel High or
Two-Wheel High, your vehicle must be stopped or
moving less than 3 mph (5 km/h) with the transmission in
NEUTRAL (N) for an automatic transmission or the clutch
pedal pressed for a manual transmission. The preferred
method for shifting out of Four-Wheel Low is to have your
vehicle moving 3 mph (5 km/h).
Press and release the Two-Wheel High or Four-Wheel
High switch. You must wait for the Two-Wheel High or
Four-Wheel High indicator light to stop flashing and
remain on before shifting your transmission into gear
or releasing the clutch pedal.
If the Four-Wheel High switch is pressed when your
vehicle is in gear and/or moving, the Four-Wheel High
indicator light will flash for 30 seconds but will not
complete the shift unless the vehicle is moving slower
than 3 mph (5 km/h) and the transmission is in
NEUTRAL (N).
Shifting into NEUTRAL
{ CAUTION:
Shifting the transfer case to NEUTRAL
can cause your vehicle to roll even if the
transmission is in PARK (P). You or someone
else could be seriously injured. Be sure to set
the parking brake before placing the transfer
case in NEUTRAL. See Parking Brake on
page 2-52.
To shift the transfer case to NEUTRAL, first make sure
the vehicle is parked so that it will not roll:
1. Set the parking brake.
2. Start the vehicle or turn the ignition to RUN.
3. Press the foot brake pedal and put the transmission
in NEUTRAL (N).
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