GM – CAMARO 1982-1992 – Repair Guide (Checked by WxMax) 287
DRIVE TRAIN
MANUAL TRANSMISSION
UNDERSTANDING THE MANUAL TRANSMISSION
Because of the way an internal combus tion engine breathes, it can produce
torque (or twisting force) only withi n a narrow speed range. Most overhead
valve pushrod engines must turn at about 2500 rpm to produce their peak
torque. Often by 4500 rpm, they are prod ucing so little torque that continued
increases in engine speed produce no power increases.
The torque peak on overhead camshaft engines is, generally, much higher, but
much narrower.
The manual transmission and clutch are employed to vary the relationship
between engine RPM and the speed of the w heels so that adequate power can
be produced under all circumst ances. The clutch allows engine torque to be
applied to the transmission input shaft gradually, due to mechanical slippage.
The vehicle can, consequently, be star ted smoothly from a full stop.
The transmission changes the ratio between the rotating speeds of the engine
and the wheels by the use of gears. 4-speed or 5-speed transmissions are most
common. The lower gears al low full engine power to be applied to the rear
wheels during acceleration at low speeds.
The clutch driveplate is a thin disc, the center of which is splined to the
transmission input shaft. Both sides of the disc are covered with a layer of
material which is similar to brake li ning and which is capable of allowing
slippage without roughness or excessive noise.
The clutch cover is bolted to the engine flywheel and incorporates a diaphragm
spring which provides the pressure to engage the clutch. The cover also houses
the pressure plate. When the clutch pe dal is released, the driven disc is
sandwiched between the pressu re plate and the smooth surface of the flywheel,
thus forcing the disc to turn at th e same speed as the engine crankshaft.
The transmission contains a mainshaft which passes all the way through the
transmission, from the clutch to the dr iveshaft. This shaft is separated at one
point, so that front and rear portions can turn at different speeds.
Power is transmitted by a countershaft in the lower gears and reverse. The
gears of the countershaft mesh with gear s on the mainshaft, allowing power to
be carried from one to the other. Countershaft gears are often integral with that
shaft, while several of the mainshaft gea rs can either rotate independently of
the shaft or be locked to it. Shifting from one gear to the next causes one of the
gears to be freed from rotating with the shaft and locks another to it. Gears are
locked and unlocked by internal dog clutc hes which slide between the center of
the gear and the shaft. The forward gears us ually employ synchronizers; friction
