GPA30 - PTO clutch and brake


The multidisc clutch (15) is fitted in the PTO housing at the rear of the GPA30 transmission centre housing. It transmits engine speed to the driving pinions and combined driven pinions, via a proportional solenoid valve controlled by the tractor electronic system. The multidisc clutch consists of the following main components:


• a unit (6) supported by two bearings fitted in a unit/driving pinions assembly;
• a sleeve (10) force fitted into the unit (6). This sleeve performs two functions:
- at the rear, it feeds the multidisc clutch (17 bar low pressure) and lubricates the friction discs through independent ports and channels.
- at the front, it supports the drive hub (1) ball bearing (13).
• two segments (22), which ensure the oil tightness of the 17 bar low pressure circuit;
• a cover (32) fixed to the clutch unit and enclosing:
- the friction discs splined to the hub (1),
- the intermediate plates integral with the cover via catches.

Power take-off PTO clutch 


Clutch engaged position The clutch is fed by:
- the 17 bar low pressure circuit;
- the proportional solenoid valve (1) located on the right-hand hydraulic cover;
- an external pipe going from the right-hand hydraulic cover to the rear PTO housing.


The pressurised oil enters the sleeve (10) through channel A and flows to hydraulic chamber B and channel C. The pressure pushes the progressivity washer (5) and piston (19). The piston (19) compresses the friction discs (4) splined to the hub (1) and the intermediate plates (3) integral with the cover (32) via catches. The movement provided by the layshafts is thus transmitted to the driving pinions via the unit (6). Lubrication of the friction discs A channel D at the centre of the sleeve (10) lubricates the friction discs in clutch engaged position.

Clutch disengaged position

When the solenoid valve no longer feeds the clutch, the piston (19) is pressed against the housing (6) by the spring (8). The oil in the piston (19) hydraulic chamber is directed to the return by the solenoid valve. Simultaneously, the ball of valve (7) leaves its seat, thus assisting the pressure release of the piston (19) hydraulic chamber.

Power take-off PTO brake 


The cylinder of PTO brake piston (1) is located on the rear partition of the centre housing (45). It is held in place by means of Mecanindus pins. When the proportional solenoid valve feeds the PTO clutch, the piston (19) is pressurised (clutch engaged position). The brake piston (1) is at rest. The upper and lower PTO shaftlines can then rotate freely. When the proportional solenoid valve no longer feeds the PTO clutch, the piston (19) is at rest (declutched position). 


The 17 bar low pressure is directed to the brake. It moves the piston (1), which presses against the rim of the unit (6), thus braking the upper and lower PTO shaftlines. Lubrication of the power take off brake A restrictive channel at the centre of the piston (1) lubricates the rim of the unit (6) when braking.

Parts list 
(1) Drive hub (2) Bearing cone (3) Intermediate plates (4) Friction discs (5) Progressivity washer (6) Clutch housing (7) Valve (8) Spring (9) O’ring (10) Sleeve (11) Screw (12) Chamfered washer (13) Ball bearing (14) Circlip (15) Clutch unit assembly (16) Screw (17) Spring seat (18) O’ring (19) Piston
(20) Support (21) O’ring (22) Sealing rings (28) Secondary shaft (29) Restrictor (30) Threaded plug (31) Oil deflector (32) Cover

Parts list 
(1) Drive hub (3) Intermediate plates (4) Friction discs (5) Progressivity washer (6) Clutch housing (7) Valve (8) Spring (9) O’ring (10) Sleeve (11) Screw (12) Chamfered washer (13) Ball bearing (14) Circlip (15) Clutch unit assembly (16) Screw (17) Spring seat (18) O’ring (19) Piston (20) Support
(21) O’ring (22) Sealing rings (29) Restrictor (30) Threaded plug (31) Oil deflector (32) Cover

Disassembling and reassembling the clutch unit assembly

Remove the block consisting of the clutch unit (15) and unit/driving pinion(s) (23) assemblies. Split assemblies.

Disassembly 
Tighten unit (6) in a vice fitted with soft jaw protectors.
Loosen the screws (16). Separate cover (32) from unit (6). Remove the friction discs (4) and intermediate plates (3).


Using a locally made tool, hold the hub (1). Loosen the screw (11) and remove the chamfered washer (12). Release the spring (8). Remove the tool.
Remove the drive hub (1), spring seat (17), spring (8), support (20) and progressivity washer (5). If necessary, remove the circlip (14) and extract the ball bearing (13).


Drive the piston (19) off the unit (6) using compressed air. Remove the O'rings (9) (18) (21). If necessary, on the unit (6):
- extract the sleeve (10);
- drive off the valve (7).

Reassembly 
Clean and check all components. Replace any defective parts.


If the valve (7) had to be removed:
- Fit the valve on the unit (6).
- Check that the valve is operating correctly by rapidly shaking the unit several times: the movement of the ball in the valve must be heard.


If the sleeve (10) had to be removed:
- Check that the restrictor (29) is present on the sleeve.
- Lightly smear the sleeve with Loctite 648 or equivalent. Fit it into the unit (6) using a press. Clean off any excess Loctite.
- Using compressed air, check that the 17 bar low pressure channel is not obstructed with Loctite.
- Lightly smear the plug (30) thread with Loctite 242 or equivalent. Tighten this plug moderately.

Lubricate with clean transmission oil:
- the new O'rings (9) (18) (21);
- the rim of the sleeve (10);
- the piston (19).


Equip:
- the piston (19) with seal (18);
- the sleeve (10) with seals (9) (21).
Fit the piston into the unit (6) by gradually and alternately striking around its top rim with a plastic mallet. Ensure there are no seal fragments after fitting.
Fit the bearing (13) into the drive hub (1). Refit the circlip (14).
If removed, refit the oil deflector (31) in the drive hub.


Refit:
- the progressivity washer (5) according to the position indicated;
- the support (20);
- the spring (8);
- the spring seat (17);
- the drive hub (1) with its components.
Compress the spring (8) using the tool.

Refit the chamfered washer (12), positioning its chamfer correctly.
Lightly smear the thread of the screw (11) with Loctite 270 or equivalent. Tighten this screw to a torque of 24 - 28 Nm.
Soak the friction discs (4) for a few minutes in a clean transmission oil bath. Before assembly, ensure the oil has reached all parts of the discs.
Alternately fit on the drive hub (1), the friction discs (4) and intermediate plates (3) removed during operation: start by placing an intermediate plate (3) against the support (20).


Rotate the intermediate plates (3) to align the tabs T according to V. Position the cover (32). Lightly smear the thread of the screws (16) with Loctite 242 or equivalent. Tighten these screws to a torque of 25.5 - 34.5 Nm.


Manually check that the drive hub (1) rotates freely in the cover (32).


Assemble and refit the block consisting of the clutch unit (15) and unit/driving pinion(s) (23) assemblies.