GMC 2003 GMT560 T-Series Owner's Manual page 52

Rear Air Suspension Dump Control
If your vehicle is equipped with single-axle air
suspension, you may have this control. The air
suspension dump control allows the operator to lower
the deck height approximately 4.5 inches (11.5 cm) from
the normal frame height.
Press the bottom of the switch to deflate the air
suspension and lower the deck height. Press the top of
the switch to return the suspension to normal deck
height.
An indicator light will come on and stay on whenever
the switch is in the dumped position.
2-16
The switch to deflate and
inflate the air suspension
is located in the instrument
panel switchbank.
Automatic Transmission Operation
We build vehicles with five and six-speed automatic
transmissions. This part of the manual covers the basics
of these. With these transmissions, you will find an
®
Allison Transmission Operator's Manual in your vehicle
that goes into more detail. On the headliner, in front
of and above the driver, or in some other place near the
driver, you will see a label that describes important
operating facts about the automatic transmission in
your vehicle. Make sure you follow the instructions on
this label.
{
CAUTION:
It can be dangerous to get out of your vehicle
without the parking brake firmly set. Your
vehicle can roll. If you've left the engine
running, the vehicle can move suddenly. You
or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set the parking brake.