Chevrolet 2004 Silverado 1500 Pickup Owner's Manual page 127

An indicator on the bezel near the lever shows you the
transfer case settings:
2-Wheel High (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.
4-Wheel High (4HI): Use 4HI 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.
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CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the
transmission is in PARK (P), or if you have a
manual transmission, even if you are in gear.
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 2-44 .
NEUTRAL (N): Shift to this setting only when your
vehicle needs to be towed. See Recreational Vehicle
Towing on page 4-53 or Towing Your Vehicle on
page 4-53 .
4-Wheel Low (4L0): This setting also engages your
front axle and 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.
You can shift from 2-Wheel High (2HI) to 4-Wheel High
(4HI) or from 4-Wheel High (4HI) to 2-Wheel High
(2HI) while the vehicle is moving. Your front axle will
engage faster if you take your foot off of the accelerator
for a couple of seconds after you shift. In extremely
cold weather, it may be necessary to stop or slow the
vehicle to shift into 4-Wheel High (4HI).
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