GMC Sierra 2014 Owner's Manual page 306

9-42 Driving and Operating
While in Four-Wheel Drive High
or Four-Wheel Drive Low you
may experience reduced fuel
economy.
Avoid driving in four-wheel drive
on clean, dry pavement. It may
cause your tires to wear faster,
make the transfer case harder to
shift, and run noisier.
If the transfer case shift lever is
in the N (Neutral) position and
you have difficulty reaching the
selected transfer case mode,
with the engine running, shift the
transmission momentarily to
D (Drive) and then back to
N (Neutral). This will realign the
gear teeth in the transfer case
and allow you to complete
the shift.
Shifting from Two-Wheel Drive
High to Four-Wheel Drive High
Shifts between Two-Wheel Drive
High and Four-Wheel Drive High
can be made at any vehicle
speed.
Shift the transfer case shift lever
in one continuous motion into
either the Four-Wheel Drive High
or Two-Wheel Drive High
position.
Shifting from Two-Wheel Drive
High to Four-Wheel Drive High
while the vehicle is in motion
may require that moderate force
be applied to the shift lever for a
few seconds before Four-Wheel
Drive High can be engaged,
especially in cold weather.
In extremely cold weather, it may
be necessary to slow or stop the
vehicle to shift into Four-Wheel
Drive High.
While in Four-Wheel Drive High,
the vehicle can be driven at any
posted legal speed limit.
Shifting In or Out of Four-Wheel
Drive Low
Caution
Shifting the transfer case into
Four-Wheel Drive Low while
moving at speeds faster than
5 km/h (3 mph) 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 Drive Low while the
vehicle is moving faster than
5 km/h (3 mph).
Shifting into Four-Wheel Drive
Low should be done, if possible,
with the vehicle at a slight roll,
5 km/h (3 mph) or less.
Shift the transmission into
N (Neutral).