GMC 2007 Sierra - Manual (Page 166)

Shifting from Two-Wheel Drive High or
Four-Wheel Drive High to Four-Wheel
Drive Low
To shift from Two-Wheel Drive High or Four-Wheel
Drive High to Four-Wheel Drive 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 Drive Low
is to have your vehicle moving 3 mph (5 km/h).
Press and release the Four-Wheel Drive Low
switch. You must wait for the Four-Wheel Drive
Low indicator light to stop flashing and stay
on before shifting the transmission into gear or
releasing the clutch pedal.
Notice: Shifting the transmission into gear
before the Four-Wheel Drive Low indicator light
has stopped flashing could damage the
transfer case. To help avoid damaging your
vehicle, always wait for the Four-Wheel
Drive Low indicator light to stop flashing
before shifting the transmission into gear.
If the Four-Wheel Drive Low switch is pressed
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 slower than 3 mph
(5 km/h) and the transmission is in NEUTRAL (N).
The transfer case will shift to Four-Wheel Drive
High while waiting to complete the shift.
It is normal to hear and feel your vehicle’s transfer
case shift into Four-Wheel Drive Low. If you shift
with the vehicle stopped, the indicator light may
continue to flash slowly. It may be necessary to shift
the transmission momentarily into REVERSE (R)
and DRIVE (D), for an automatic transmission, or
REVERSE (R) and FIRST (1) for a manual
transmission to make the light stop flashing.
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