GMC SIERRA 2002 Manual page 111

DRIVE (D): This position is for normal driving. If you
need more power for passing, and you're:
D
Going less than about 35 mph (55 km/h), push your
accelerator pedal about halfway down.
D
Going about 35 mph (55 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
driving. You may want to shift the transmission to
THIRD (3) or, if necessary, a lower gear selection if the
transmission shifts too often.
NOTICE:
If your vehicle is equipped with the Allison
Transmission, do not idle in DRIVE (D) for more
than five minutes. Extended idling in DRIVE (D)
may cause transmission overheating and damage.
Always select PARK (P) if idle time is longer than
five minutes.
2-30
If your vehicle is equipped with the Allison
Transmission, it will initially attain first range when
DRIVE (D) is selected. As vehicle speed increases, the
transmission will upshift automatically through each
available range up to FIFTH (5). As the vehicle slows,
the transmission will downshift automatically.
THIRD (3): This position is also used for normal
driving, however it offers more power and lower fuel
economy than DRIVE (D).
-
road
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.