GMC 2006 Sierra - Manual (Page 143)

Shifting from Two-Wheel High or
Four-Wheel High to Four-Wheel Low
Notice: Shifting the transfer case into
Four-Wheel Low while moving at speeds faster
than 3 mph (5 km/h) may cause premature wear to
the transfer case, and may cause the gears to grind.
To avoid causing premature wear, and grinding the
gears, do not shift the transfer case into Four-Wheel
Low while the vehicle is moving faster than
3 mph (5 km/h).
To shift from Two-Wheel High or Four-Wheel High
to Four-Wheel Low, the 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 into four-wheel low is to have your
vehicle moving 3 mph (5 km/h).
Press and release the Four-Wheel Low switch. You
must wait for the four-wheel low indicator light to stop
flashing and stay on before shifting your transmission
into gear or releasing the clutch pedal.
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.
If the Four-Wheel Low switch 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 slower than
3 mph (5 km/h) and the transmission is in NEUTRAL (N).
The transfer case will shift to Four-Wheel High while
waiting to complete the shift.
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