GMC Sierra Classic 2007 Owner's Manual page 153

An indicator light near the lever shows you the
transfer case settings:
Notice: Driving on clean, dry pavement in
four-wheel drive for an extended period of time
can cause premature wear on your vehicle's
powertrain. Do not drive on clean, dry
pavement in Four-Wheel Drive for extended
periods of time.
4L (Four-Wheel Low): This setting also engages
the front axle and delivers extra torque. You
may never need 4L. It sends maximum power to
all four wheels. You might choose 4L if you
are driving off-road in deep sand, deep mud, deep
snow, and while climbing or descending steep
hills. When operating in 4L, the gear ratio provides
additional torque when compared to 4H. The
transmission gear shift feel will be exaggerated.
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 168.
N (Neutral): Shift to this setting only when your
vehicle needs to be towed. See Recreational
Vehicle Towing on page 418 or Towing Your
Vehicle on page 417.
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