GMC TopKick 2007 Owner's Manual page 121

Shifting Out of Four-Wheel Low
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) and the
engine running. The preferred method for shifting
out of Four-Wheel Low is to have your vehicle
moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the knob
to Four-Wheel High or Two-Wheel High. You
must wait for the Four-Wheel High or Two-Wheel
High indicator light to stop flashing and remain
on before shifting the transmission into gear.
Notice: Shifting the transmission into gear
before the Four-Wheel High or Two-Wheel High
indicator light has stopped flashing could
damage the transfer case. To help avoid
damaging your vehicle, always wait for the
Four-Wheel High or Two-Wheel High indicator
light to stop flashing before shifting the
transmission into gear.
If the knob is turned to Four-Wheel High or
Two-Wheel High while your vehicle is in gear
and/or moving, the Four-Wheel High or Two-Wheel
high indicator light flashes for 30 seconds. It will
not complete the shift unless your vehicle is
moving less than 3 mph (5 km/h) with the
transmission in NEUTRAL (N).
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