Figure 2-3.-Cross section of a disc clutch.
Figure 2-4.-Disc clutch operation.
Figure 2-5.-Clutch linkage.
2-3
transmission transfers engine power from the clutch
shaft to the propeller shaft and allows the operator to
change the gear ratio between the engine and the rear
wheels.
Dual-ratio, or two-speed rear axles are often used
on trucks. They have two gear ratios that can be chosen
by the operator, usually by a manual control lever. A
dual-ratio rear axle works the same as the auxiliary
transmission; it doubles the number of gear ratios for
driving the vehicle under the various loads and on
different roads.
The most common transmission type is the
synchromesh transmission. The synchromesh
transmission is basically a constant mesh, collar-shift
transmission with an extra device, called a synchronizer,
to equalize the speed of the mating parts before they
engage. The synchronizer is used in all manual
automotive transmissions and is common in other
equipment where shifting while moving is required.
Part of the prestart operation is to check the fluid
level in the manual transmission. The normal level of
lubricant is usually at the bottom of the filler plug
opening. When lubricant is needed, you should always
check the operators manual for the location and type of
lubricant required for the transmission. When you keep
the lubricant level correct, the gear teeth are protected,
foam is reduced, and the transmission runs smoothly.
Some transmission troubles that you may encounter
and must document are as follows:
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l
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Hard shifting
Slipping out of gear
No power through the transmission
Transmission noisy when in gear
Gear clash in shifting
Oil leaks
Manual Shift Operation
Skill in manual shifting is a requirement of
professional driving. Poor manual shifting results in
poor vehicle performance and can cause vehicle
damage. Know the gearshift lever positions so well that
you can shift to any gear without looking at the shift
lever. The gearshift pattern is usually diagramed in the
vehicle or in the operators manual. Never move the
gearshift lever from one position to another while the
engine is running until you have fully depressed the