chapter 4 & 5 clutches

8/6/2019 Chapter 4 & 5 Clutches

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Clutches


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Bolted to Crank

(friction disk) splined to transmissionInput shaft

(throw-out bearingT/O bearing) allowsto push on rotatingclutch fingers

Bolted to flywheel - Appliesthe spring force to clamp thefriction disk to the flywheel

(clutch fork) pushes

T/O bearing to releaserotating clutch

Pilot bushing or bearing in centerof flywheel or crankshaft, supports

the end of input shaft


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Purpose of the Clutch

Allows engine to be disengagedfrom

transmission for shifting gears and comingto a stop

Allows smooth engagementof engine to

transmission


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Basic purpose

Used to disengage engine from input shaft

FlywheelBolted to crankshaft

Provides surface for clutch disc to work on

Clutch disc Splined to transmission input shaft

Fits between flywheel and pressure plate


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Flywheel bolts

to crankshaft

Pressure plate & coverbolt to flywheel

If there is a chance you will be reusingpressure plate, make alignment marksto flywheel to maintain proper balanceBEFORE removal

When unbolting pressure plate from theflywheel, remove bolts evenly as not tobend the cover. REMEMBER, this isunder high spring pressure.


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Flywheel


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Flywheel

Acts as engine balancer

Works with crank balancer to smooth out firingpulses

Some will be balanced to engine

Adds inertia to engine rotation

Works as heat sink for clutch

Ring gear for starter engagement

Some vehicles have dual mass flywheel


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Flywheels Add weight to crank for non-power strokes

Has ring-gear for cranking engine (usually replaceable)


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Flywheel service Visually inspect for hot spots, grooves,

scoring and cracks

Check with dial indicator for runout andcrank end play

Most flywheels can (should) be resurfaced

Must remove dowel pins

Inspect ring gear


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Flywheels

Hot spots


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Flywheel service Flywheel should be marked before

removing to maintain balance

On Front wheel drive cars a lot ofFlywheels are used for Ignition timing

marks. They should be marked before

removing. Some will only bolt on one waydont take the chance MARK IT


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Checking Flywheel for Run-out


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Flex plates Ring gear for automatic transmissions

Light weight, bolts crank to torque converter

Sometimes toolight weight


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Clutch disc


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Splines to input shaft

Of transmission

Clutch Disk or

Friction Disk


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Clutch disc

Friction material disc splined to input shaft

Friction material may contain ASBESTOS Friction material can be bonded or riveted

Friction is attached to wave springs

Most have torsional dampener springs Normal wearing component

Normally a worn out disc will cause

slipping


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Clutch disc service

Inspect for wear similar to brake pads

Common to have loose or broken springs

Common failure due to oil contamination Must find cause BEFORE repair

Normally purchased in kit containing

pressure plate, disc, throw out bearing


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Clutch disc service Clutch disc will normally have a flywheel

side

Disc must be centered with clutch

alignment tool before pressure plate bolteddown

Make sure new disc fits on input shaft of the

transmission before you install it


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Friction disks

Often made of

asbestos Must be put in

only one way

Usually marked

Clutch wont

release if wrong


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Friction disks

Torsional springs

Can be spring or rubber

Dampen power impulses from crankshaft


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Friction disks

Cushion springs

Waved metal between clutch half's

Dampen clutch engagement


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Torsional SpringsHas pins to limit amount of twist.

Springs try to keep it centered between pins.

Springs sometimes get weak and start rattling or fall out


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Clutch disksFriction material isnt very thick.Minimum thickness around .012


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Pressure plate


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Construction of

theP

ressureP

late

Coil spring pressure plate

(cover and pressure plate)


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Pressure plate

Provides clamping pressure to disc

Works like spring loaded clamp Bolted to _________________

Can use Belleville spring acted on by

Throw Out bearing Can use coil springs and levers acted on by

Throw Out bearing


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Types of Clutches (pressure plates)

Coil spring

9 spring 12 spring

3 fingers for T/O

bearing to push on


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Diaphragm-Spring Clutches


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Centrifugal Clutch

T/O bearing

Pressure plate


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Centrifugal Clutch


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Pressure plate service

Mark relation to flywheel if reused

Remove bolts slowly in criss-cross pattern Inspect fingers for parallelism, cracking or

uneven wear

Inspect friction surface for hot spots, cracksetc and with straight edge for warpage

Must be torqued to specs and in sequence

Uses hard bolts


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Checking pressure plate for

warpage


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Release/ throw out bearing


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Throw out Bearing (release bearing) Slides on transmission input shaft bearing

retainer


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Throw out bearings


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Release/ throw out bearing

Acted on by clutch fork - acting on pressure

plate

Moves toward flywheel when pedal pushed

Slides on front portion of transmission

called bearing retainer

Normally not in contact with pressure plate

until pedal pushed


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Throw out bearings

Most need clearance between fingers of pressure

plate so it isnt spinning all the time (free play)

Riding the clutch (foot resting on pedal)

Pushes T/O bearing into pressure plate fingers

Causes it spin constantly

Wearing it out too soon

Releases some of clutch spring pressure

Causing clutch to slip


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Slipping clutch ?


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Free play

Clearance between T/O bearing and clutchfingers

Measured at clutch pedal

Usually 1 inches of free movement

Goes away as clutch disk wears thinner

Some manufactures use T/O bearings thatalways ride on the clutch fingers

Usually self adjusting


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Release bearing service

Very common failure - isolated by lightly

applying clutch and listening

Inspect for looseness or roughness

Most are sealed but some were lubeable

Clutch fork must be lubed at pivot point and

bearing contact points

Bearing retainer and input shaft should be

lubed

Clutch fork must be secured at the pivot point


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Pilot Bushing or bearing

READ ON


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Pilot bearing / bushing

Used on some cars

Supports front of transmission input shaft Can be needle bearing or bronze bushing

May be part of clutch kit


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Pilot servicing

Should always be changed with clutch

Can be isolated by applying clutch in gear Special pullers may be used for removal

Can be removed with grease

Should be lightly lubed on installation


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Clutch linkage

Can be operated by cable, rods or

hydraulics

May be automatic or manually adjusted

Hydraulic will have a master and slave

cylinder

Will use brake fluid for hydraulic action

Will need bleeding with repairs


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Clutch Linkage Can be very complicated

Have the right amount of

movement and directionwithout too much pedalpressure

Wear

Motor mounts Spring to pull T/O bearing

away

Has to be lubricated


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Over-center spring Helps pull up on

clutch pedal

Helps pull down on

clutch pedal


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Clutch fork

T/O bearinghooks here

Fulcrum point

Clutch fork wear


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Hydraulic clutch

Uses master cylinder and slave cylinder

Uses brake fluid Must be bled


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Hydraulic clutch No complicated

linkage

Can easily controlmechanicaladvantage withpiston sizes

Self lubricating No motor mount

problemsService just like you would hydraulicbrakes


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Slave cylinder

Some are adjustable

for free-play andsome not


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Fords slave cylinders

Some are part of T/O

bearing

Cant change without pulling

tranny (inside bellhousing)


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Cable clutch

No complicated

linkage

Flexibility

No motor mount

problems


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Linkage/Cable/Hydraulic controls


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Clutch Safety Switch

Prevents from cranking with clutch engaged

Some standard transmissions wont let youtake the key out and lock the steering

column with out the transmission in reverse

Prevents steering lock while moving forward


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Clutch Disk Replacement

Very wise to:

Have flywheel surfaced (even with no run-out orhot spots)

Replace pilot bushing or bearing

Replace T/O bearing

Replace pressure plate (cover, plate springs)


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Clutch Disk Replacement

Very wise to inspect & replace as

necessary:

Clutch fork & pivot

Input shaft bearing retainer on transmission

(where T/O bearing slides)

Linkage, cable or hydraulic components

Motor mounts

Flywheel ring gear


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Installing new clutch Drive in pilot bushing or bearing with

bushing driver


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Installing new clutch

Loctite and torque flywheel to

specifications on a clean crankshaft hub


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Installing new clutch

You must use clutch alignment tool (pilot

shaft) when bolting up pressure plate

Torque and Loctitepressure plate to

specifications

Use a crossing pattern to pull pressure plate

down evenly


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Universal clutch alignment tool

Select end that fits tight in pilot bushing or

bearing


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Clutch Alignment tools (pilot shaft)


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Alignment studs

Cut off bolts

screwed into

engine block

Prevents from

bending clutch

disk wheninstalling

transmission


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Adjust clutch Shorten or lengthen linkage or cable to

reach proper free-play

Jam nut

Adjusting nut


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CLUTCH PROBLEM

DIAGNOSIS The more information you have, the easier it

is to properly diagnose it.

Talk to the customer, ask questions.

Road test the vehicle with the customer

driving, if possible.

Look for driving habits that cause failure.

Listen carefully to changes in the noise.


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CLUTCH SLIPPAGE Engine speed increases vehicle speed does not.

Slipping is caused by:

Improper adjustment (too tight)

Weak pressure plate springs

Worn disc

Contamination of the disc (oil)

Adjustment clearance decreases with disc wear.


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CLUTCH CHATTER Clutch chatter is a shaking or shuddering.

Clutch chatter is cause by:

Broken motor mounts

Glazed clutch disc

Loose mounting bolts

Worn pilot bushing


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OTHER CLUTCH NOISES Most clutch noises are caused by bearings

and bushings.

Bushings squeal or howl.

Bearings grumble or grate.

Misalignment is a common cause of clutch

problems.


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CLUTCH VIBRATES Clutch vibration can occur at any clutch

position.

Can feel the vibration, and sometimes

hear it also.

Loose flywheel bolts

Flywheel runout

Imbalanced flywheel or pressure plate


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DRAGGING CLUTCH Dragging results from the clutch not

completely disengaging.

Maximum spin down time 5 seconds.

Dragging is caused by:

Warped disc or Pressure plate

Loose disc facingIncorrect clutch pedal adjustment.

Defective release lever


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PULSATING CLUTCH PEDAL Pedal pulsations a rapid up-and-down

movement of the clutch pedal as the clutch

engages or disengages. Pulsating is caused by:

Broken, bent, or warped release levers.

Misaligned bell housing.Warped pressure plate, disc, or flywheel.


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BINDING CLUTCH Clutch pedal does not operate smoothly.

Possible causes of binding are:

Worn front bearing retainer.

Dirty or worn input shaft splines.

Bent or worn linkage.


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The End

chapter 4 & 5 clutches

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