Automatic Transmission Operation - GMC 2005 T-Series Owner's Manual

On the highway, with the rear axle in low range and the
transmission in top gear, you may shift the rear axle
to high range by raising the switch and releasing
the accelerator momentarily. Reapply the accelerator
after you shift.
Under light load conditions, first shift the rear axle into
the high range with the vehicle at a standstill and
then operate the transmission normally.

Automatic Transmission Operation

GM builds 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.
2-16
CAUTION:
{
It can be dangerous to get out of your vehicle
without the parking brake firmly set. Your
vehicle can roll. If you have left the engine
running, the vehicle can move suddenly. You or
others could be injured. To be sure your vehicle
will not move, even when you are on fairly level
ground, always set the parking brake.
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.