GMC 2005 Sierra 1500 Pickup Owner's Manual page 131

Recommended Transfer Case Settings
Driving
Conditions
2HI
Normal YES
Variable
Severe
Extreme
Vehicle in
Tow*
*See "Recreational Vehicle Towing" in the Index for
further information.
You can choose among four driving settings:
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 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.
Transfer Case Settings
AUTO
4HI 4LO
4WD
YES
YES
YES
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.
N
G
(4HI): Use 4HI when you need extra traction, such
a 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.
g
(4LO): This setting also engages your front axle and
YES
delivers extra torque. You may never need 4LO. 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. When
operating in 4LO, the gear ratio is extra deep when
compared to 4HI. The transmission gear shift feel will be
exaggerated.
2-41