GMC 2005 Envoy Owner's Manual page 102

Automatic Transfer Case
2HI (Two-Wheel High): This setting is for driving in
most street and highway situations. Your front axle is not
engaged in two-wheel drive. It also provides the best
fuel economy.
A4WD (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 2HI.
4HI (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.
2-28
If your vehicle is equipped
with four-wheel drive, the
transfer case knob is
located to the right of the
steering wheel on the
instrument panel. Use this
knob to shift into and
out of four-wheel drive.
4LO (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.
CAUTION:
{
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 2-31.
NEUTRAL: Shift the vehicle's transfer case to
NEUTRAL only when towing your vehicle. See
Recreational Vehicle Towing on page 4-50 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.