GMC 1996 Sierra Owner's Manual page 84

The front axle portion of the indicator diagram will light
up when you shift into four-wheel drive.
Some delay between shifting and the indicator's lighting
is normal. If the indicator light does not light up, or if
the front axle light does not go out after you shift out of
four-wheel drive, have your dealer check your system.
An indicator near the lever shows you the transfer
case settings:
2H (2-Wheel High): This setting is for driving in most
street and highway situations. Your front axle is not
engaged in two-wheel drive.
4H (4-Wheel High): This setting engages your front
axle to help drive your vehicle. Use 4H when you need
extra traction, such as on wet or icy roads, or in most
off-road situations.
N (Neutral): Shift to this setting only when your vehicle
needs to be towed or when using a power take-off.
4L (4-Wheel Low): This setting also engages your front
axle to give you extra power, but should be used only
for off-road driving.
You can shift from 2-WHEEL HIGH (2H) to 4-WHEEL
HIGH (4H) or from 4-WHEEL HIGH (4H) to
2-WHEEL HIGH (2H) while the vehicle is moving. Your
front axle will engage hster if you take your foot off of
the accelerator for a few seconds after you shift. In
extremely cold weather,
it
may be necessary to stop or
slow the vehicle
l o
shift out of 2-WHEEL HIGH (2H).
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