exj_6.pdf

CLUTCH

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CLUTCH

TABLE OF CONTENTS

page

DESCRIPTION AND OPERATION

CLUTCH ................................1

FLYWHEEL ..............................2

CLUTCH DISC............................2

CLUTCH PRESSURE PLATE .................2

CLUTCH RELEASE BEARING ................3

HYDRAULIC CLUTCH LINKAGE ..............4

DIAGNOSIS AND TESTING

SAFETY PRECAUTIONS ....................4

INSTALLATION METHODS AND PARTS

USAGE ................................4

CLUTCH DIAGNOSTIC INFORMATION .........4

CLUTCH CONTAMINATION ..................6

IMPROPER CLUTCH RELEASE OR

ENGAGEMENT ..........................6

CLUTCH MISALIGNMENT...................6

CLUTCH HOUSING MISALIGNMENT ..........6

CLUTCH FLYWHEEL RUNOUT ...............6

CLUTCH COVER AND DISC RUNOUT .........7

CLUTCH DIAGNOSIS CHARTS ...............7

SERVICE PROCEDURES

CLUTCH COMPONENT LUBRICATION .........9

CLUTCH LINKAGE FLUID ...................9

CLUTCH FLUID LEVEL....................10

FLYWHEEL .............................10

REMOVAL AND INSTALLATION

CLUTCH COVER AND DISC ................11

RELEASE BEARING ......................12

PILOT BEARING .........................12

CLUTCH HOUSING .......................13

CLUTCH HYDRAULIC LINKAGE .............13

SPECIFICATIONS

TORQUE ...............................15

DESCRIPTION AND OPERATION

CLUTCH

DESCRIPTION

The clutch mechanism consists of a flywheel, a sin-

gle, dry-type disc, and a diaphragm style clutch cover

(Fig. 1). A hydraulic linkage is used to operate the

clutch release bearing and fork. The flywheel is

bolted to the rear flange of the crankshaft. The

clutch pressure plate is bolted to the flywheel with

the clutch disc located between these two compo-

nents. The clutch system provides the mechanical,

but still easily detachable, link between the engine

and the transmission. The system is designed to

ensure that the full torque output of the engine is

transfered to the transmission while isolating the

transmission from the engine firing pulses to mini-

mize concerns such as gear rattle.

OPERATION

Leverage, clamping force, and friction are what

make the clutch work. The disc serves as the friction

element and a diaphragm spring and pressure plate

provide the clamping force. The clutch pedal, hydrau-

lic linkage, release lever and bearing provide the

leverage.

Fig. 1 Engine Powerflow

6 - 2

CLUTCH

DESCRIPTION AND OPERATION (Continued)

The clutch master cylinder push rod is connected

to the clutch pedal. When the clutch pedal is

depressed, the slave cylinder is operated by the

clutch master cylinder mounted on the dash panel.

The release fork is actuated by the hydraulic slave

cylinder mounted on the transmission housing. The

release bearing is operated by a release fork pivoting

on a ball stud mounted in the transmission housing.

The release bearing then depresses the pressure

plate spring fingers, thereby releasing pressure on

the clutch disc and allowing the engine crankshaft to

spin independently of the transmission input shaft

(Fig. 2).

Fig. 3 Flywheel

1 – CRANKSHAFT

2 – RING GEAR

3 – FLYWHEEL

OPERATION

The flywheel serves to dampen the engine firing

pulses. The heavy weight of the flywheel relative to

the rotating mass of the engine components serves to

stabilize the flow of power to the remainder of the

drivetrain. The crankshaft has the tendency to

attempt to speed up and slow down in response to

the cylinder firing pulses. The flywheel dampens

these impulses by absorbing energy when the crank-

shaft speeds and releasing the energy back into the

system when the crankshaft slows down.

CLUTCH DISC

DESCRIPTION

The clutch disc friction material is riveted to the

disc hub (Fig. 4). The hub bore is splined for installa-

tion on the transmission input shaft. The clutch disc

has cushion springs in the disc hub to dampen disc

vibrations during application and release of the clutch.

Fig. 2 Clutch Operation

1 – FLYWHEEL

2 – PRESSURE PLATE FINGERS

3 – PIVOT POINT

4 – RELEASE BEARING PUSHED IN

5 – CLUTCH DISC ENGAGED

6 – CLUTCH DISC ENGAGED

7 – RELEASE BEARING

OPERATION

The clutch disc is held onto the surface of the fly-

wheel by the force exerted by the pressure plate’s dia-

phragm spring. The friction material of the clutch disc

then transfers the engine torque from the flywheel and

pressure plate to the input shaft of the transmission.

FLYWHEEL

DESCRIPTION

The flywheel (Fig. 3) is a heavy plate bolted to the

rear of the crankshaft. The flywheel incorporates the

ring gear around the outer circumference to mesh

with the starter to permit engine cranking. The rear

face of the flywheel serves as the driving member to

the clutch disc.

CLUTCH PRESSURE PLATE

DESCRIPTION

The clutch pressure plate assembly is a diaphragm

type with a one-piece spring and multiple release fin-

gers (Fig. 5). The pressure plate release fingers are

preset during manufacture and are not adjustable.

The assembly also contains the cover, pressure plate,

and fulcrum components.

CLUTCH

6 - 3

DESCRIPTION AND OPERATION (Continued)

OPERATION

The clutch pressure plate assembly clamps the

clutch disc against the flywheel. When the release

bearing is depressed by the shift fork, the pressure

exerted on the clutch disc by the pressure plate

spring is decreased. As additional force is applied,

the bearing presses the diaphragm spring fingers

inward on the fulcrums. This action moves the pres-

sure plate rearward relieving clamp force on the disc.

The clutch disc is disengaged and freewheeling at

this point.

CLUTCH RELEASE BEARING

DESCRIPTION

A conventional release bearing (Fig. 6) is used to

engage and disengage the clutch pressure plate

assembly. The clutch release bearing is mounted on

the transmission front bearing retainer. The bearing

is attached to the release fork, which moves the bear-

ing

into

contact

with

the

clutch

cover

diaphragm

spring.

Fig. 4 Clutch Disc-Typical

1 – FACING MATERIAL

2 – DAMPER SPRINGS

3 – HUB

Fig. 6 Clutch Release Bearing

1 – RELEASE BEARING

2 – RELEASE FORK

OPERATION

The release bearing is operated by a release fork in

the clutch housing. Slave cylinder force causes the

release lever to move the release bearing into contact

with the diaphragm spring. As additional force is

applied, the bearing presses the diaphragm spring

fingers inward on the fulcrums. This action moves

the pressure plate rearward relieving clamp force on

the disc. Releasing pedal pressure removes clutch

hydraulic pressure. The release bearing then moves

away from the diaphragm spring which allows the

pressure plate to exert clamping force on the clutch

disc.

Fig. 5 Clutch Pressure Plate-Typical

1 – COVER

2 – RELEASE FINGERS

3 – PRESSURE PLATE

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CLUTCH

DESCRIPTION AND OPERATION (Continued)

HYDRAULIC CLUTCH LINKAGE

COMPONENTS. BREATHING EXCESSIVE CONCEN-

TRATIONS OF THESE FIBERS CAN CAUSE SERIOUS

BODILY HARM. WEAR A RESPIRATOR DURING SER-

VICE AND NEVER CLEAN CLUTCH COMPONENTS

WITH COMPRESSED AIR OR WITH A DRY BRUSH.

EITHER CLEAN THE COMPONENTS WITH A WATER

DAMPENED RAGS OR USE A VACUUM CLEANER

SPECIFICALLY DESIGNED FOR REMOVING ASBES-

TOS FIBERS AND DUST. DO NOT CREATE DUST BY

SANDING A CLUTCH DISC. REPLACE THE DISC IF

THE FRICTION MATERIAL IS DAMAGED OR CON-

TAMINATED. DISPOSE OF ALL DUST AND DIRT CON-

TAINING ASBESTOS FIBERS IN SEALED BAGS OR

CONTAINERS. THIS WILL HELP MINIMIZE EXPOSURE

TO YOURSELF AND TO OTHERS. FOLLOW ALL REC-

OMMENDED SAFETY PRACTICES PRESCRIBED BY

THE OCCUPATIONAL SAFETY AND HEALTH ADMIN-

ISTRATION (OSHA) AND THE ENVIRONMENTAL

SAFETY AGENCY (EPA), FOR THE HANDLING AND

DISPOSAL OF PRODUCTS CONTAINING ASBESTOS.

DESCRIPTION

The hydraulic linkage consists of a clutch master

cylinder with integral reservoir, a clutch slave cylin-

der and an interconnecting fluid line (Fig. 7).

The clutch master cylinder push rod is connected to

the clutch pedal. The slave cylinder push rod is con-

nected to the clutch release fork. The master cylinder is

mounted on the driver side of the dash panel adjacent

to the brake master cylinder and booster assembly.

INSTALLATION METHODS AND PARTS USAGE

Distortion of clutch components during installation

and the use of non-standard components are common

causes of clutch malfunction.

Improper clutch cover bolt tightening can distort

the cover. The usual result is clutch grab, chatter

and rapid wear. Tighten the cover bolts as described

in Removal and Installation section.

An improperly seated flywheel and/or clutch hous-

ing are additional causes of clutch failure. Improper

seating

Fig. 7 Clutch Master Cylinder

1 – CAP

2 – FILL LINE

3 – CLUTCH MASTER CYLINDER

4 – RESERVOIR

will

produce

misalignment

and

additional

clutch problems.

The use of non-standard or low quality parts will

also lead to problems and wear. Use recommended

factory quality parts to avoid comebacks.

A cocked pilot bearing is another cause of clutch

noise, drag, hard shifting, and rapid bearing wear.

Always use an alignment tool to install a new bear-

ing. This practice helps avoid cocking the bearing

during installation.

OPERATION

The clutch linkage uses hydraulic pressure to oper-

ate the clutch. Depressing the clutch pedal develops

fluid pressure in the clutch master cylinder. This

pressure is transmitted to the slave cylinder through

a connecting line. In turn, the slave cylinder operates

the clutch release lever.

Slave cylinder force causes the release lever to

move the release bearing into contact with the dia-

phragm spring. As additional force is applied, the

bearing presses the diaphragm spring fingers inward

on the fulcrums. This action moves the pressure

plate rearward relieving clamp force on the disc.

CLUTCH DIAGNOSTIC INFORMATION

Unless the cause of a clutch problem is obvious, accu-

rate problem diagnosis will usually require a road test to

confirm a problem. Component inspection (Fig. 8) will

then be required to determine the actual problem cause.

During a road test, drive the vehicle at normal

speeds. Shift the transmission through all gear

ranges and observe clutch action. If chatter, grab,

slip, or improper release is experienced, remove and

inspect the clutch components. However, if the prob-

lem is noise or hard shifting, further diagnosis may

be needed as the transmission or another driveline

component may be at fault. Careful observation dur-

ing the test will help narrow the problem area.

DIAGNOSIS AND TESTING

SAFETY PRECAUTIONS

WARNING: EXERCISE CARE WHEN SERVICING

CLUTCH COMPONENTS. FACTORY INSTALLED

CLUTCH DISCS DO NOT CONTAIN ASBESTOS

FIBERS. DUST AND DIRT ON CLUTCH PARTS MAY

CONTAIN ASBESTOS FIBERS FROM AFTERMARKET

CLUTCH

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DIAGNOSIS AND TESTING (Continued)

Fig. 8 Clutch Components And Inspection

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