GMC T-Series 1999, Owner'S Manual, Page: 60 / 344

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Automatic Transmission Third Gear Hold
(If Equipped)
If your vehicle has this feature, your range selector has a
“2
-
3” position. You can’t shift up to the next higher gear
when the transmission is in this position unless your
engine
-
governed speed is exceeded, such as when
going downhill.
This feature is useful for certain load and traffic
conditions or when plowing snow. See the Allison
Automatic Transmission Operator’s Manual in your
vehicle for further information.
Manual Transmission Operation
This part of the manual covers the basics of the manual
transmission. With some of the transmissions, you will find
another manual in your vehicle that goes into more detail.
Using the Clutch
When you’re starting to move the vehicle, it’s important
to begin with the engine speed at idle. Then start to
engage the clutch and listen for an engine speed drop of
about 100 rpm. At this point, the clutch is engaging, so
you should increase the engine speed and fully engage
the clutch. It’s important not to increase the engine
speed sooner or before the clutch engages. If you do,
you can cause damage to your vehicle.
Double-Clutching
You must use the “double
-
clutching” method when you
shift an unsynchronized gear set. Simply disengage the
clutch, shift to NEUTRAL and engage the clutch. When
you’re shifting down to a lower gear, accelerate the
engine speed while in NEUTRAL to get ready for the
lower gear.
5- and 6-Speed Transmissions
These transmissions have gears that automatically
synchronize when you shift up or down
(except FIRST (1) gear on the five
-
speed transmission,
which is unsynchronized). Choose the gear which will
maintain the road speed you want while keeping the
engine above two
-
thirds of the governed speed. When
the engine speed drops below two
-
thirds of the
governed speed, shift into the next lower gear before
your engine begins to lug. When you shift down, be sure
to double
-
clutch if required.