flywheel LAND ROVER DISCOVERY 2002 Service Manual

CLUTCH - V8
DESCRIPTION AND OPERATION 33-2-7
Flywheel
The flywheel is bolted to a flange on the rear of the crankshaft with six bolts. A dowel on the crankshaft flange ensures
that the flywheel is correctly located. A ring gear is fitted on the outside diameter of the flywheel and seats against a
flange. The ring gear is an interference fit on the flywheel and is installed by heating the ring and cooling the flywheel.
The ring gear is a serviceable item and can be replaced if damaged or worn.
The operating face of the flywheel is machined to provide a smooth surface for the drive plate to engage on. Three
dowels and six threaded holes provide for the location and attachment of the pressure plate. The flywheel is balanced
to ensure that it does not produce vibration when rotating. A machined slot, with a series of holes within the slot, is
located on the engine side of the flywheel. The slot accommodates the tip of the crankshaft position sensor which is
used by the Engine Control Module (ECM) for engine management.

+ ENGINE MANAGEMENT SYSTEM - V8, DESCRIPTION AND OPERATION, Description - engine
management.
Pressure plate
1Leaf spring
2Fulcrum ring
3Fulcrum ring
4Drive plate
5Pressure plate6Diaphragm
7Cover
8Rivet
9Retractor clip
The pressure plate assembly comprises a pressure plate, cover and diaphragm and is mounted on and rotates with
the flywheel.

CLUTCH - V8
33-2-8 DESCRIPTION AND OPERATION
The pressure plate is forged from cast iron and machined to provide a smooth surface for the drive plate to engage
on. Three lugs on the outer diameter of the pressure plate connect it via three leaf springs to the cover. The leaf
springs have two tempered steel leaves which assist in pulling the pressure plate away from the drive plate when the
clutch pedal is depressed.
The cover is made from pressed steel and houses and locates all pressure plate components. Shouldered rivets
support the diaphragm and fulcrum rings inside the cover. The cover also provides attachment for balance weights
when the pressure plate assembly is balanced. Three holes in the cover locate on the dowels on the flywheel and six
further holes provide for the attachment of the cover to the flywheel with six bolts and spring washers. Larger holes
in the cover provide ventilation for the drive plate and pressure plate and flywheel contact surfaces.
The diaphragm comprises a cast ring with eighteen fingers. The diaphragm is attached to the cover with nine
shouldered rivets. Two circular steel fulcrum rings are also secured by the shouldered rivets on each side of the
diaphragm. The fulcrum rings allow the diaphragm to pivot between them when the clutch is depressed or released.
When pressure is applied to the diaphragm fingers by the release bearing, the diaphragm pivots between the fulcrum
rings and moves away from the pressure plate. Retractor clips are secured to the pressure plate and are located on
the outer diameter of the diaphragm. The retractor clips ensure that the diaphragm remains in contact with the
pressure plate.
Drive plate
1Friction material
2Hub
3Damper spring
4Retainer plate
5Disc adaptor
6Stop pin

CLUTCH - V8
DESCRIPTION AND OPERATION 33-2-9
The drive plate is of the spring centred type and is sandwiched between the pressure plate and the flywheel. The drive
plate has a splined hub which engages with the splines on the primary drive shaft from the gearbox. The hub is located
in an inner plate which contains six compression damper springs. A spring retainer plate and a disc adaptor are
secured together with stop pins which limit the angular deflection of the disc adaptor. Engine power is transmitted from
the disc adaptor to the damper springs. The damper springs then transfer the power to the retainer plate and the hub.
Friction washers are located between the hub, retainer plate and disc adaptor and provide further damping.
A spring steel plate is riveted to the disc adaptor and provides the attachment surface for the drive plate friction
material. The friction material comprises discs which are secured with rivets to each side of the plate. The rivets are
installed through recessed holes in the disc and emerge in recessed holes in the opposite disc. The drive plate is 267
mm (10.5 in) diameter and has a friction material manufactured from APTEC T385.

CLUTCH - V8
33-2-10 DESCRIPTION AND OPERATION
Operation
Hydraulic operation
Refer to illustration.

+ CLUTCH - V8, DESCRIPTION AND OPERATION, Hydraulic operation.
When the clutch pedal is depressed, the master cylinder piston is pushed into the master cylinder. The movement of
the piston pressurises the fluid in the master cylinder, forcing the pressurised fluid into the hydraulic feed pipe to the
slave cylinder. The hydraulic pressure is felt at the slave cylinder piston which moves under the hydraulic force
applied, pushing the clutch release lever via the piston rod.
When the clutch pedal is released, the force applied to the release lever by the fingers of the diaphragm, moves the
release lever, which pushes the slave cylinder piston into the cylinder. The displaced hydraulic fluid is pushed up the
hydraulic feed pipe and returned to the master cylinder.
Mechanism operation
When the clutch pedal is depressed, hydraulic pressure extends the piston and rod in the slave cylinder. The
extension of the piston pushes the rod against the outer end of the release lever which pivots around the ball spigot.
The inner end of the release lever pivots towards the engine applying pressure to the release bearing. The release
bearing slides along the release bearing sleeve and pushes on the fingers of the diaphragm. The diaphragm pivots
about the fulcrum rings in the cover. As the diaphragm is deflected, it removes pressure from the pressure plate. The
pressure plate moves away from the drive plate assisted by the three leaf springs and retractor clips.
The removal of force from the pressure plate on the drive plate reduces the friction between the flywheel, drive plate
and pressure plate. The drive plate slips between the flywheel and the pressure plate preventing rotary movement
being transferred from the flywheel and pressure plate to the primary driveshaft.
When the clutch pedal is released, hydraulic force is removed from the piston in the slave cylinder. This allows the
fingers of the diaphragm to push the release bearing along the release bearing sleeve. The movement of the release
bearing moves the release lever which pivots on the ball spigot, pushing the piston and rod back into the slave
cylinder.
The removal of pressure from the release bearing on the diaphragm, causes the diaphragm to pivot around the
fulcrum rings in the cover. The force applied to the pressure plate from the diaphragm overcomes the force of the leaf
springs and the pressure plate moves towards the drive plate and flywheel.
The pressure plate applies pressure to the drive plate which is pushed against the flywheel. As the clutch pedal is
progressively released, the friction between the drive plate, flywheel and pressure plate increases. The increase in
friction transfers the rotary movement of the flywheel and pressure plate to the drive plate which in turn starts to rotate
the primary driveshaft. When the clutch pedal is released fully, the force applied by the diaphragm to the pressure
plate forces the drive plate onto the flywheel with no slippage.

CLUTCH - V8
REPAIRS 33-2-13
REPAIRS
Clutch assembly
$% 33.10.01
Remove
1.Remove gearbox assembly.

+ MANUAL GEARBOX - R380,
REPAIRS, Gearbox - V8.
2.Restrain flywheel.
3.Working in diagonal sequence, progressively
loosen 6 bolts securing clutch cover to flywheel.
Remove bolts.
4.Remove clutch cover.
5.Remove clutch plate.
6.Renew all worn or damaged components.Refit
1.Clean clutch cover and flywheel mating faces
and spigot bush in end of crankshaft.
2.Fit LRT-12-001 to spigot bearing in crankshaft.
3.Fit clutch plate onto LRT-12-001, ensure side
marked 'flywheel side' is against flywheel.
4.Fit clutch cover and locate on dowels.
5.Fit clutch cover bolts and progressively tighten,
in diagonal sequence shown, to 40 Nm. (30
lbf.ft).
6.Fit gearbox assembly.

+ MANUAL GEARBOX - R380,
REPAIRS, Gearbox - V8.