GMC 2008 Envoy Denali Owner's Manual page 104

AUTO (Automatic Four-Wheel Drive): This setting is
ideal for use when road conditions are variable. When
driving your vehicle in automatic four-wheel drive, the
front axle is engaged, but the vehicle's power is sent to
the rear wheels. When the vehicle senses a loss of
traction, the system will automatically engage four-wheel
drive. Driving in this mode results in slightly lower fuel
economy than Two-Wheel High.
m
4 (Four-Wheel High): This setting should be used
when you need extra traction, such as on snowy or
icy roads or in most off-road situations. This setting also
engages your front axle to help drive your vehicle.
n
4 (Four-Wheel Low): This setting also engages
your front axle and delivers extra torque. It sends
maximum power to all four wheels. You might choose
this setting if you are driving off-road in deep sand,
deep mud, and climbing or descending steep hills.
2-30
CAUTION:
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Shifting the transfer case to NEUTRAL
can cause your vehicle to roll even if the
transmission is in PARK (P). You or someone
else could be seriously injured. Be sure to set
the parking brake before placing the transfer
case in NEUTRAL. See Parking Brake on
page 2-33.
NEUTRAL: Shift the vehicle's transfer case
to NEUTRAL only when towing your vehicle.
See Recreational Vehicle Towing on page 4-40
for more information.
An indicator light in the knob will show you which
position the transfer case is in. The indicator lights will
come on briefly when you turn on the ignition and one will
stay on. If the lights do not come on, you should take your
vehicle to your dealer for service. An indicator light will
flash while shifting the transfer case. It will stay on when
the shift is complete. If for some reason the transfer case
cannot make a requested shift, it will return to the last
chosen setting.
If the service Four-Wheel Drive Warning Light on the
instrument panel cluster stays on, you should take
your vehicle to your dealer for service. See Service
Four-Wheel Drive Warning Light on page 3-47 for
further information.