Manual Transmission Operation - GMC TopKick 2007 Owner's Manual

Overdrive Defeat
If your vehicle has this feature, you can select not
to shift up to fifth gear. This is useful when
towing or under a heavy load.
Press the switch to limit the transmission to
fourth gear. This will allow for fewer downshifts
while pulling a trailer or under a heavy load. The
indicator light in the switch will come on
whenever overdrive defeat is active.
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The overdrive defeat
switch is located in the
instrument panel to
the right of the
steering column.

Manual Transmission Operation

Using the Clutch
When you are starting to move the vehicle, it is
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 is important not to increase the
engine speed sooner or before the clutch begins
its engagement. 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. Disengage
the clutch, shift to NEUTRAL and engage the
clutch. When upshifting, slow the engine until the
engine rpm and road speed match. When
downshifting, accelerate the engine until the
engine rpm and road speed match. Then quickly
disengage the clutch and move the shift lever
to the next gear position and engage the clutch.