Specifications, Service and Repair of Farm and Lawn Tractors


Pressure clutch multidisc type

The engine clutch system installed on the Heavy gearboxes equipping tractors is of the oil-immersed multidisc type.

The hydraulic clutch - which transmits the movement - is similar to a Direct-drive clutch but is larger. This clutch is controlled by an hydraulic valve mounted on the right-hand side of the gearbox, itself actuated by the clutch master-cylinder.

Clutch construction

The clutch assembly is installed between the flywheel and the transmission shaft of the Dynashift unit. Main shaft (7) penetrates closing plate (10) which separates the flywheel from the transmission fluid.

Shaft (7) is in constant engagement with the damper fixed on the flywheel. Due to the splines, it is rotates together with clutch housing (23) which includes intermediate plates (45) and which houses piston (46).

Drive hub (37) comprising discs (44) is integral with clutch shaft (33).

Fixed unit (12) has two functions:

- it receives the 17-bar pressure,
- it serves as the lubrication and cooling pump body (30 l/min, rated pressure 0.4 bar).

The pump supply is obtained from the centre housing via a 500-micron strainer (replaceable), tube (17) placed under the transmission, and a second tube (20).

Depending on the type, the clutch assembly comprises a different number of discs and intermediate plates:

- 6 discs, 6 intermediate plates
- 7 discs, 7 intermediate plates
- 8 discs, 8 intermediate plates.

Discs (44) have a paper lining for smoother engagement and reduced noise.


When the clutch pedal is released, the hydraulic valve located on the right-hand side of the gearbox delivers a pressure of 17 bar which moves piston (46); the latter in turn compresses intermediate plates (45) against discs (44), entraining clutch shaft (33).

The valve monitors the smoothness and progressive engagement of the clutch, and modulates the pressure applied on the piston.


Once the pressure is no longer applied, piston (46) is pushed back by Belleville washers (42), and intermediate plates (45) are no longer in contact with the discs.

The lubrication and cooling flow to the discs is interrupted in the declutched position to avoid driving the discs by drag effect.

For the same reason, the discs have a face curved to facilitate disengagement.

Parts list

1-O’rings, 2-Backup washers, 3-Splined bush, 4-Locking ring, 5-Screw, 6-Washer, 7-Main shaft, 8-O’ring, 9-Shim(s), 10-Closing plate, 11-Pump cover, 12-Pump body, 13-Dynashift cover, 14-O’ring, 15-O’rings, 16-Spacer, 17-Tube, 18-Screw, 19-Flange, 20-Tube, 21-Spacer casing, 22-Screw, 23-Clutch housing, 24-Pin, 25-Flange, 26 -Screw, 27-Dust shield, 28-O’ring, 29-O’ring, 30-Seal holder, 31-Screw, 32-Direct-drive shaft, 33-Clutch shaft, 34-Circlip, 35-Washer, 36-Bearing, 37-Drive hub, 38- Screw, 39-Clutch cover, 40-Bearing, 42-Belleville washers, 43-Circlip, 44-Disks, 45-Intermediate plates, 46-Piston, 47-Clutch assembly, 48-Seal, 49-Seal, 50-Bearing, 51-Bush, 52-Seal rings, 53-Lubricating pump, 54-Screw, 55-Bearing, 56-Circlip, 57-Lip seal, 58-Circlip, 61-Centring pin, 62-Screw, 63-Finger, 64-Union, 65-Tube, 66-Union, 67-Diagnostic connector, 68-1.5-bar valve, 69-O’ring, 70-Tube, 71-O’ring, 72-Union, 73-Plug, 74-500 micron strainer, 75-O’ring, 76-Plug, 77-Indexing port

Removing and refitting the closing plate and replacing lip seal (57) and O’ring (1)

Split the tractor between the engine and gearbox.

Drain the gearbox.

In order to facilitate unsticking of closing plate (10), install two jacking screws of sufficient length in the tapped holes in the closing plate, then remove the disc.

Remove front circlips (58) and remove splined bush (3), backup washers (2) and seal (1).

Extract seal (57).

Fit seal (57) using a suitable fixture.

Place O’ring (1) between rings (2). Reinstall splined bush (3). Replace front circlip (58) and position correctly in the groove.

Ensure presence of centring pins (61) and shims (9).

Replace O’ring (8).

Coat tapped-hole surrounds with Loctite 5206.

Grease the lip of seal (57). Place protector P/N 3378012M2 on shaft (7). Screw two guide studs in opposing locations on the spacer and reinstall closing plate (10), with finger (63) in the slot of pump body (12) (Fig28).

Install long screws (62) in the same holes as those provided for centring pins (61). Install screws (5), torque to 36 - 46 Nm.

Service the oil in the sumps and check on the sight glass located on the left of the centre housing.

Reassemble the tractor between the engine and gearbox and check adjustment of the chassis reinforcements (if installed).

Removing and refitting the clutch

Split the tractor between the engine and gearbox.

Drain the gearbox and the intermediate housing.

Visually identify the contour of the plugs. If the tractor is fitted with chassis reinforcements, it may be necessary to remove the right-hand reinforcement.

Remove tube (17).

Remove closing plate (10). Repeat operation 3.

Remove tube (20).

Remove union (72) and tubes (70) and (65).

Remove clutch (47) using the locally manufactured tool.

Replace O’rings (14) and (69).

Replace O’rings (15) and (71).

Refit tubes (20) (65) (70) and union (72).

Coat feeler gauges (9) used at operation 45 with miscible grease, and place on pump cover (11).

Refit feed tube (2) (Fig29).

If disassembled, coat finger (63) with Loctite 270 and screw into closing plate (10).Ensure presence of centring pins (61). Replace O’ring (8).Clean and coat hole surrounds with Loctite 5206. Refit the closing plate.

Fit screws (5) (62) with washers (6) then insert and torque to 25 - 35 Nm.

The two long screws (62) are installed with centring pins (61).

Replace O’rings (28) (29). Reinstall seal holder (30). Install screws (31) and torque to 14 -20 Nm.

Replace dust shield (27). Reinstall tube (17) and flanges (19) and (25), ensuring that groove G in flange (25) is aligned with the face of seal holder (30) (Fig.30). Tighten screw (26). Torque screws (31) and (38) to 25 -3 5 Nm. If disassembled, reinstall and adjust the right-hand chassis reinforcement.

Service the oil in the sumps and check on the sight glass located on the left of the centre housing.

The drain plug in the intermediate housing is special. It has a cylindrical part that is missing on the other plugs. It is therefore essential to observe the position during reassembly.

Reassemble the tractor between the engine and gearbox.

Bleed the clutch control valve and check the clutch lubrication pressure.

Check the operation of the direct-drive clutch.

Road-test the engine clutch.

Check the leak tightness of flange (19) and seal holder (30).

Remove the clutch and Direct-drive shaft (32).

Temporarily refit clutch assembly (47) onto clutch shaft (33), using the tool used at operation 22 (and temporarily excluding the direct-drive shaft). Place 2 mm feeler gauge (9) on cover (11).

Grease the lip of seal (57). Slide protector 3378012M2 over the splines of shaft (7) to protect the seals. Screw two studs in opposing locations on the spacer and reinstall closing plate (10). Install and tighten a few of the screws.

Adjusting the clutch

This operation consists in obtaining an axial clearance of J1 = 0.60 to 0.80 mm between pump cover (11) and closing plate (10) (Fig.31)

Install a dial-gauge comparator on the end of shaft (7) and check the play by moving the clutch assembly sideways.

Ensure bearing (36) in the clutch assembly is fully abutted against cover (13) before pulling
on the shaft (Fig.31)

Remove closing plate (10); depending on the measured clearance, select thickness of feeler gauges (9) to obtain a clearance J1 of between 0.6 and 0.8 mm.

Remove the clutch and reinstall Direct-drive shaft (32), turning the undercut part (designed to receive spring R towards the rear axle (Fig.32).

Proceed to final refitting of the clutch assembly.

Disassembling and reassembling the clutch

Remove the clutch and place in the vertical position, that is, cover (39) resting on a suitable fixture.

Remove front circlip (58). Remove bush (3), rings (2) and seal (1).

Remove circlip (56). Remove pump cover (11) and bearing (55).

Extract lubrication pump (53) from pump body (12). Separate the pump body from clutch housing (23).

Remove seal rings (52).

If necessary, extract bush (51) and disassemble 1.5- bar valve (68).

Separate clutch housing (23) from cover (39). Remove discs (44) and intermediate plates (45).

Remove drive hub (37).

If necessary, extract bearing (36).

Using a suitable fixture, compress Belleville washers (42). Remove rear circlip (58) (Fig.34). Remove locking ring (4). Untension the Belleville washers.

Separate clutch housing (23) from shaft (7). Remove the Belleville washers.

Remove piston (46). If necessary, extract bearing (50).

If necessary, remove circlip (43) and bearing (40).

Ensure presence of pin (24).

If it was removed, refit bearing (50), using a suitable fixture.

Install seals (48) (49).

Install piston (46).

The angular position of the piston depends on that of the lubrication ports of clutch housing (23). Align the indexing holes drilled in the unit and piston (Fig.33). Proceed by inserting a suitable diameter pin. Finish refitting the piston by progressively tapping around the edge, using a plastic hammer. Ensure no seal fragment remains after assembly.

If it was removed, refit bearing (40), using a suitable fixture, the sealed face pointing towards the Dynashift. Fit circlip (43).

On tractors fitted with the Heavy gearbox, the hydraulic engine clutch comprises six Belleville washers.

Fit Belleville washers (42) on shaft (7) (Fig.34).

Slide clutch housing (23) onto clutch shaft (7).

Compress the Belleville washers using the tool used at operation 57. Locate bush (4) by aligning the two flats with those on clutch housing (23). Replace rear circlip (58) and properly position in bottom of groove.

If it was removed, fit bearing (36) using a suitable fixture; ensure the sealed face is facing the Dynashift. Install the hub and the bearing inside cover (39).

Soak the discs in a bath of transmission fluid for approximately one hour. Check they are totally impregnated. Depending on the type, the number of discs and intermediate plates is different, as well as the length of the splines on drive hub (37) and the thickness of cover (39).

Position intermediate plates (45) and discs (44) on drive hub (37), by aligning the respective recesses.

Place clutch housing (23) assembly on cover (39). Torque screws (22) to 25.5 - 34.5 Nm.

Check by hand that drive hub (37) is free to rotate.

Check that seal rings (52) turn correctly in their grooves. Coat the seal rings with miscible grease then install, ensuring that they do not project beyond the contour of the unit.

If it was removed, torque-tighten the 1.5-bar valve to 47 - 54 Nm. Next coat the outside diameter of bush (51) with Loctite 270 then fit the bush using a suitable fixture. Ensure chamfer C is oriented as shown in Fig.10.

After fitting the bush, check that the oil pressure ports are not blocked with Loctite. Clean and lubricate the bush. Assemble pump body (12) to clutch housing (23).

Lubricate pump (53) and set it by orienting the flats with those of clutch housing (23). Manually check the angular travel of the rotor against the flats on clutch housing (23).

Refit pump cover (11). Fit bearing (55). Fit circlip (56). Torque screws (54) to 36 -46 Nm.

Fit O’ring (1) and rings (2). Repeat operation 7. Reinstall the clutch.

Removing and refitting control valve

Drain the gearbox (Fig.29).

Remove any neighbouring parts likely to hinder removal of the valve. Disconnect tubes (1) and (2), hose (3), and the connectors to solenoid valves EV1 and EV2 (mark connector positions).

Remove the valve.

Clean the mating surfaces. Coat the one on the gearbox housing with sealing compound.

Replace the O’rings on the 17-bar transfer tubes. Reinstall the valve. Coat screws (5) with sealing compound, install, and torque to 25-35 Nm.

Reconnect the tubes, the hose and the connectors.

Service the oil in the sumps and check the level on the sight glass located on the left-hand side of the center housing.

Bleed the clutch control valve.

Check the valve regulating pressure.

Reinstall any items previously removed from around the valve.

Check the sealing of the mating face and the couplings, and operation of the Dynashift.