Four-Wheel Drive; Front Axle Locking Feature - GMC 2005 Sierra 1500 Pickup Owner's Manual

While you accelerate, it is normal for the light to go on
and off if you quickly change the position of the
accelerator.
If your vehicle has four-wheel drive and is equipped with
a manual transmission, disregard the SHIFT light when
the transfer case is in 4-Wheel Low.
Ignore the SHIFT light when you downshift.

Four-Wheel Drive

If your vehicle has four-wheel drive, you can send your
engine's driving power to all four wheels for extra traction.
To get the most satisfaction out of four-wheel drive, you
must be familiar with its operation. Read the part that
follows before using four-wheel drive. See the
appropriate text for the transfer case in your vehicle.
Notice: Driving on clean, dry pavement in
four-wheel drive for an extended period of time may
cause premature wear on your vehicle's powertrain.
Do not drive on clean, dry pavement in four-wheel
drive on pavement for extended periods of time.

Front Axle Locking Feature

The front axle locks and unlocks automatically when
you shift the transfer case. Some delay for the axle to
lock or unlock is normal.
Manual Transfer Case
The transfer case shift lever is on the floor to the right
of the driver. Use this lever to shift into and out of
four-wheel drive.
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