7-2 DRIVE TRAIN
MANUAL TRANSMISSION
Understanding the Manual Transmission
Because of the way an internal combustion engine breathes, ii can
produce torque (or twisting force) only within a narrow speed range.
Most overhead valve pushrod engines must turn at about 2500 r )m to
produce their peak torque. Often by 4500 rpm, they are producing 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 r jlation-
ship between engine RPM and the speed of the wheels so that adequate
power can be produced under all circumstances. The clutch allow; engine
torque to be applied to the transmission input shaft gradually, due to
mechanical slippage. The vehicle can, consequently, be started 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 tra ismis-
sions are most common. The lower gears allow 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 spline
transmission input shaft. Both sides of the disc are covered with a
material which is similar to brake lining and which is capable of a
slippage without roughness or excessive noise.
The clutch cover is bolted to the engine flywheel and incorporat ;s a
diaphragm spring which provides the pressure to engage the clutclh. The
cover also houses the pressure plate. When the clutch pedal is reliased, the
driven disc is sandwiched between the pressure plate and the smoioth sur-
face of the flywheel, thus forcing the disc to turn at the same speei as the
engine crankshaft.
The transmission contains a mainshaft which passes all the K <
through the transmission, from the clutch to the driveshaft. This s taft 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 averse.
The gears of the countershaft mesh with gears on the mainshaft, a 1 lowing
power to be carried from one to the other. Countershaft gears are often
integral with that shaft, while several of the mainshaft gears can ei her
rotate independently of the shaft or be locked to it. Shifting from oie gear
to the next causes one of the gears to be freed from rotating with I le shaft
and locks another to it. Gears are locked and unlocked by internal dog
clutches which slide between the center of the gear and the shaft. Tie for-
ward gears usually employ synchronizers; friction members which
smoothly bring gear and shaft to the same speed before the toothe J dog
clutches are engaged.
Back-up Light Switch
REMOVAL & INSTALLATIONExtension Housing Seal
REMOVAL & INSTALLATIONLocate and unscrew the back-up light switch from the transmis: ion
housing. Carefully thread the new switch and tighten to 27 ft. Ibs. 37
Mm),
\. Using a seal puller, remove the oil seal from the extension housing.
Lubricate the seal with transmission oil and drive the new oil seal into the
housing.Manual Transmission Assembly
REMOVAL & INSTALLATIONI See Figures 1 thru 6- Disconnect the negative battery cable. Wait at least 90 seconds to
perform any work on models equipped with air bags.
** CAUTION
Some models covered by this manual may be equipped with a
Supplemental Restraint System (SRS), which uses an air bag.
Whenever working near any of the SRS components, such as the
impact sensors, the air bag module, steering column and instru-
ment panel, disable the SRS, as described in Section 6.- Drain the transmission fluid.
- Raise the vehicle and support safely.
- Remove the starter motor. Matchmark the driveshafts-to-flange and
remove the front (4WD) and rear driveshafts.
bolts.
7.
8.
9.- Remove the clutch release cylinder, hose and bracket.
Remove the exhaust pipe bracket which is retained by four
Disconnect the control cables/bracket and speed sensor wiring.
Remove the engine-to-transmission stiffener plate.
Place a suitable transmission jack under the transmission.- Remove the engine rear mounting bolts and raise the rear side of the
engine. - Remove the engine-to-transmission bolts, pull the transmission
toward the rear and extract.
To install: - Align the input shaft with the clutch disc and push the transmission
fully into position. - Install the transmission bolts and tighten to 53 ft. Ibs. (72 Nm).
- Install the rear engine mounts and stiffener plate. Tighten the bolts
to 27 ft. Ibs. (37 Nm). - Connect the speed sensor and control cables.
- Install the exhaust pipe bracket and tighten to -37 ft. Ibs. (51
Nm). - Install the clutch release cylinder, starter and driveshafts. Tighten
the starter to 41 ft. Ibs. (56 Nm) and driveshaft bolts to 20 ft. Ibs. (25
Nm). - Lower the vehicle.
- Connect the battery cable and refill with transmission fluid.