GMC 2004 Yukon XL Owner's Manual page 123

You can choose among four driving settings:
h
(2HI): This setting is used for driving in most street
and highway situations. Your front axle is not engaged
in two-wheel drive. This setting also provides the
best fuel economy.
AUTO 4WD: This setting is ideal for use when road
conditions are variable. When driving your vehicle
in AUTO 4WD, the front axle is engaged, but the
vehicle's power is sent only 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.
G
(4HI): Use the 4HI position 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. This is the best setting
to use when plowing snow.
5
(4LO): This setting also engages your front axle
and delivers extra torque. You may never need this
setting. It sends maximum power to all four wheels. You
might choose 4LO if you are driving off-road in deep
sand, deep mud, deep snow 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 2-36.
NEUTRAL (N): Shift the vehicle's transfer case to
NEUTRAL only when towing your vehicle. See
Recreational Vehicle Towing on page 4-53 or Towing
Your Vehicle on page 4-53 for more information.
Indicator lights in the button show which setting you are
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 remain illuminated 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.
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