GMC 2003 Yukon Owner's Manual page 118

NEUTRAL (N): In this position, your engine doesn't
connect with the wheels. To restart when you're already
moving, use NEUTRAL (N) only. Also, use
NEUTRAL (N) when your two-wheel drive vehicle is
being towed.
{
CAUTION:
Shifting into a drive gear while your engine is
running at high speed is dangerous. Unless
your foot is firmly on the brake pedal, your
vehicle could move very rapidly. You could
lose control and hit people or objects. Do not
shift into a drive gear while your engine is
running at high speed.
Notice: Shifting our of PARK (P) or NEUTRAL (N)
with the engine racing may damage the
transmission. The repairs would not be covered by
your warranty. Be sure the engine is not racing
when shifting your vehicle.
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DRIVE (D): This position is for normal driving. If you
need more power for passing, and you're:
•
Going less than about 35 mph (56 km/h), push your
accelerator pedal about halfway down.
•
Going about 35 mph (56 km/h) or more, push the
accelerator all the way down.
You'll shift down to the next gear and have more power.
DRIVE (D) can be used when towing a trailer, carrying
a heavy load, driving on steep hills or for off-road driving.
You may want to shift the transmission to THIRD (3)
or, if necessary, a lower gear selection if the
transmission shifts too often.
THIRD (3): This position is also used for normal driving,
however it offers more power and lower fuel economy
than DRIVE (D).
SECOND (2): This position gives you more power but
lower fuel economy. You can use SECOND (2) on
hills. It can help control your speed as you go down
steep mountain roads, but then you would also want to
use your brakes off and on.
If you manually select SECOND (2) in a light duty
automatic transmission, the transmission will drive in
second gear. You may use this feature for reducing the
speed of the rear wheels when you are trying to start
your vehicle from a stop on slippery road surfaces.