PTO clutch


The power take-off PTO clutch, fitted at the front of the rear axle housing, is driven by a splined shaft located inside the engine clutch input shaft, which rotates integral with the engine flywheel. The PTO clutch control shaft traverses: the gearbox primary shaft, the Speedshift, the reverse shuttle and the intermediate shaft.

The clutch consists of:
- a unit (9), supported by two ball bearings (2) (7) separated by a sleeve (4) centred in a bore of the centre housing. The sleeve (27) supports the ball bearing (22), the drive hub (21) and the piston (10).
- a bell (15) including a set of discs (17) and intermediate plates (14) is fixed onto the unit. The unit (9) comprises external helical teeth that drive the hydraulic pump gear. The bearings and discs are lubricated. Depending on the model, the clutch has either 4 or 5 discs. On the 4-disc version (Fig.1), a special spacer (28) is fitted in place of the missing disc and spacer.


 1

Clutch engaged position
A 17 bar hydraulic system supplies the clutch via a PTO proportional solenoid valve located on the right-hand hydraulic cover plate. Oil enters the unit (9) via channels a and c and chamber b. It pushes the piston (10) which compresses the discs (17) against the intermediate plates (14). As the intermediate plates are attached to the bell (15) by lugs and the discs (17) are attached to the hub (21), the drive is transmitted to the drive hub (21) in which the intermediate shaft controlling the PTO driving gear is located. At the same time, the pressure acting on the PTO brake piston is cut, allowing the 540 and 1000 rpm gears of the PTO lower shaftline to turn freely. When engaging the clutch, the discs are cooled and lubricated.

PTO brake position
When the supply is cut, the spring (18) pushes the piston back against the unit (9). When the knob located in the cab is in the PTO brake position, the ON/OFF solenoid valve for the PTO brake directs the oil towards the top cover plate, which is fitted at the rear of the tractor. Pressure acts on a piston that pushes the bearing cup on the rear bearing cone, progressively immobilising the driving gear. Fit the longer end "E" or the paint mark "P" on the clutch control shaft so that it is facing towards the input housing (Fig.2).


2



Parts list
(1) Circlip (2) Bearing (3) "O" ring (4) Sleeve (5) Seal rings (6) "O" ring (7) Bearing (8) Valve (9) Clutch unit (10) Piston (11) "O" ring (12) Belleville progressivity washers (13) Support (14) Intermediate plates
A: 4-disc clutch B: 5-disc clutch (15) Bell (16) Screw (17) Discs (18) Spring (19) Spring seat (20) Snap ring (21) Drive hub (22) Bearing (23) Washer (24) Screw (25) "O" ring (26) "O" ring (27) Sleeve
(28) Special spacer (4-disc version only) (30) Pins (31) Treated washers



Removing and refitting the PTO clutch (2-speed version)


Remove the right-hand hydraulic cover plate.
Remove the PTO top cover plate located at the rear of the tractor, the driving gear and the intermediate Shaft.
Take off the retaining screw (3) from the clutch (1) using a combination wrench (for cutting and shaping as needed). Remove the latter and the spring (5).
Check and clean the components. Replace any defective parts.
Check that the "O" rings (2) and (4) are not damaged.
Install the spring (5) in the port of the PTO shaft and refit the clutch (1) by moving it fully forwards using a lever to compress the spring in order to fit the screw (3).

Clean and smear the screw (3) with Loctite 542 and tighten to 50 - 70 Nm.
Install the intermediate shaft, the driving gear and the top cover plate.
Install the right-hand hydraulic cover plate.
Check for the correct operation of the clutch, PTO brake and linkage.
Check tightness:
- of the mating faces (spool valve support, top cover plate, right-hand hydraulic cover plate)
- Hydraulic unions

Removing and refitting the PTO clutch (4-speed version)


On 4-speed version tractors (economy), removal of the PTO clutch is the same as the 2-speed version.
The only difference relates to the parts to be removed for access (i.e. driving gears and intermediate shaft).
Remove the right-hand hydraulic cover plate.
Remove the PTO top cover plate located at the rear of the tractor, the driving gear and the intermediate shaft.
Take off the retaining screw (3) of the clutch using the same equipment as that used for the 2-speed version. Remove clutch and spring (5).
Check and clean the components. Replace any defective parts.
Check that the "O" rings (2) and (4) are not damaged.

Place spring (5) in the port of the PTO shaft and refit the clutch (1) by moving it fully forwards using a lever to compress the spring in order to fit the screw (3).
Clean and smear the screw with Loctite 542 and tighten to 50 - 70 Nm.
Install the intermediate shaft, the driving gear and the rear cover plate.
Install the right-hand hydraulic cover plate.
Check correct operation of the clutch and power take-off brake.
Check tightness:
- of the mating faces (spool valve support, top cover plate, right-hand hydraulic cover plate)
- Hydraulic unions

Disassembling and reassembling the clutch


Take off the screws (16) and washers (31).
Remove the bell (15), discs (17) and intermediate plates (14).
Place the clutch unit (9) into a vice equipped with protective jaws.
Remove the "O" rings (3) (6).
Remove the circlip (1).
Extract the bearing (2) with the sleeve (4).
Take off the seal rings (5) and extract the bearing (7)
Hold the spring (18) using a makeshift tool (Fig.3).


3

Take off the screw (24) and remove the washer (23) (Fig.3). Gradually decompress the spring using the tool.
Remove the drive hub (21), the spring seat (19), the spring (18), the support (13) and the Belleville washer (12).
Take off the snap ring (20).
Extract the bearing (22).
Take out the piston (10) by hitting the clutch unit on a block of wood.
Take off the "O" rings (11) (25) (26).

The valve (8) is crimped onto the clutch unit (9). Check that the bearing moves freely by rapidly shaking the unit up and down several times. The sleeve (27), smeared with Loctite 648, is fitted using the press. If disassembly is necessary, make sure that there is no Loctite blocking the channel when reassembling. Two pins (30) are fitted in the unit (9) 10 mm from the face.

Check and clean the components and replace those that are defective.
Using a suitable fixture and a press, fit the bearing (7) home against the shoulder.
Place seal rings (5) into their grooves and hook their ends, making sure that they turn freely.
Slide the sleeve (4) over the rings and avoid damaging them. Turn the larger sleeve diameter towards the bearing (7).
Using a suitable fixture and a press, fit the bearing (2) up against the shoulder of the unit (9).
Position the circlip (1).
Replace and lubricate the "O" rings (11) (25) (26).
Lubricate the sleeve (27) and the piston (10) and fit it into the unit using a plastic hammer.
Using a suitable fixture and a press, fit the bearing (22) into the hub (21) and refit the snap ring (20).
Install the Belleville washer (12), the support (13), the spring (18), the spring seat (19) and the drive hub (21).

Compress the spring (18) with the tool (Fig.3), fit the washer (23) and tighten the screw (24) smeared with Loctite 270 to a torque of 24 - 28 Nm.
Position the spacer (if fitted), intermediate plates and discs on the hub (21).
Position the bell (15) in the two pins (30). Fit the screws (16) each fitted with a washer (31), lightly smeared with Loctite 270, and tighten to 15 - 18 Nm.
Manually check that the discs and intermediate plates are not obstructed in any way.
Lubricate and fit the "O" rings (3) (6). The rings have different diameters.
Install the clutch.