GMC SIERRA 1997 Manual page 98

$-Wheel High (4H): 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.
Neutral (N): Shift to this setting only when your vehicle
needs to be towed or when using a power take-off.
4-Wheel Low (4L): This setting also engages your front
axle to give you extra power and also gives you a higher
driveline ratio. It 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 faster 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 to shift into 4-WHEEL HIGH (4H).
To shift into or out of 4-WHEEL LOW (4L) or
NEUTRAL (N):
1. Slow the vehicle to a roll, about 1 to 3 mph (2 to
5 kmh) and shift an automatic transmission into
NEUTRAL (N), or with a manual transmission,
press the clutch pedal.
2. Shift the transfer case shift lever in one
continuous motion.
Don't pause in NEUTRAL (N) as you shift the transfer
case into 4-WHEEL LOW (4L), or your gears
could clash.
Remember that driving in 4-WHEEL HIGH (4H) or
4-WHEEL LOW (4L) may reduce fuel economy. Also,
driving in four-wheel drive on dry pavement could
cause your tires to wear faster and make your transfer
case harder to shift and run noisier.
When your headlamps or parking lamps are on,
rotate the thumb wheel next to the headlamp switch
up to brighten or down to dim your transfer case
indicator light.
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