Tractor hydraulic system - Right-hand cover plate (100 l/min)

The right-hand cover plate is fitted to the rear axle housing and has two main functions:
- it supports numerous hydraulic system components,
- it incorporates the various suction and distribution channels of the high flow rate system.
On its internal face, the cover plate is connected to the:
- hydraulic pumps of the high flow rate system and their drive gear
- suction pipe
- inlet manifold
- the left-hand cover plate transfer pipe.
On its external faces, it is connected to the:
- four or five control solenoid valves of the low pressure functions (depending on option), There is a diode in the solenoid of the PTO brake solenoid valve. The PTO clutch is controlled by an on/off solenoid valve.
- safety valve in the high flow rate system
- trailer brake valve (if fitted) or a cover plate (depending on option)
- two "diagnostics" connectors,
- suction strainer
- 15 micron main filter and support
- filter switch
- engine speed sensor
- pump coupling unit and coupling solenoid valve.

Parts list 
(1) Right-hand hydraulic cover plate (2) Pump (3) Seal (4) Suction manifold (5) Screw (6) Seal (7) Transfer pipe (8) Seal (9) Restrictor (10) Transfer pipe (11) Gear (12) Seal (13) "O" ring (14) Pin (15) Centring pin (16) Screw (17) Engine speed sensor (18) Screw (19) Elbow union (20) Seal
(21) Pin (22) Pipe (23) Plate (24) Elbow union (25) Pressure connector (26) Filter (27) PTO brake solenoid valve (28) PTO clutch solenoid valve (29) Front axle clutch solenoid valve (or plug) depending on option (30) Differential lock solenoid valve (31) Hare / Tortoise (Hi / Lo) solenoid valve
(32) Support (33) Spacer (34) Pressure switch (35) 15 micron filter (36) Pipe (37) Selection unit (38) Screw (39) Seals (40) Non-return valve (41) Elbow union (42) Pressure connector (43) Coupling solenoid valve (44) Non-return valve (45) 200 bar pressure relief valve (46) Union
(47) Plug (48) Union (49) Stud (50) Seal (51) Cover plate (52) Pressure connector (53) Plug (54) Elbow union (55) Seals (56) Hose (57) Elbow union (58) Support (59) Seal (60) Pressure connector (61) Pipe (62) Union (63) Hose (64) Elbow union (65) Trailer brake spool valve (66) Screw (67) Union
(68) Hose (69) Trailer brake connector

Removing and install the cover plate

Preliminary steps
Immobilise the tractor. Chock the left rear wheel. Apply the hand brake.
Chock between the frame and the front axle (optional).
Partially drain the rear axle housing. Take off the wheel concerned. Place an axle stand in position.

Disconnect the blockage indicator harness (34).
Remove the 15 micron filter (35) and its support (32).

Remove the strainer (26) to access the partially hidden screw.
If the tractor is fitted with a trailer brake mechanism: Remove the spool valve (65) and support (58).

Disconnect and block:
- the hose to the auxiliary system (48),
- the pipe to the linkage spool valve (46),
- the rear differential lock pipe and the hose from the front differential lock control (if fitted),
- the 4WD clutch supply pipe for tractors fitted with this option,
- the PTO brake supply pipe,
- the steering spool valve supply pipe via the 15 micron filter (35),
- the 17 bar hydraulic cover plate supply pipe.

Disconnect the harness of the engine speed sensor (17) and filter switch.
Disconnect solenoid valves (27) to (31), marking their connections. The function of each solenoid valve is indicated on the external face of the hydraulic cover plate casing. The cover plate is fitted with two different types of solenoid valves. The solenoid valve (27) of the PTO brake has a solenoid with a diode and is represented by the following symbol (+/-).
Remove the screws (18) and the cover plate (1).
After removing the cover plate, if necessary, remove the transfer pipe (7) from the housing, ensuring hydraulic continuity to the pump manifold.

Clean the mating faces of the housing and cover plate.
Check for the presence of the two centring pins (14) and rivets at the ends of the channels on the cover plate.
Install new seals:
- on the Hare / Tortoise channels,
- on the power take-off clutch channel.
Install and position the suction pipe (22), with its notch along the axis of the pin (21). Position the seal (20).

Screw two makeshift guide studs into opposing holes on the housing.
Install the transfer pipe (if removed), first checking the seals are in a good condition.
Smear the mating faces of the cover plate with a sealing product (Loctite 510 or equivalent) taking
care not to block the hydraulic ports of the Hare / Tortoise mechanism.
Reinstall the cover plate. Take out the guide studs. Install and tighten the cover plate screws to a torque of 72 - 96 Nm.
Reconnect (in accordance with the markings made):
- solenoid valves (27) to (31),
- filter switch
- engine speed sensor (17).

Attach the electrical harnesses with a retainer.
Reconnect the pipes and hoses.
Reinstall the trailer brake spool valve (65) and support (58).

Check the condition of the seal of the strainer (26) and lubricate it. Install the strainer and tighten it an additional quarter turn after it contacts with the seal. Install the 15 micron filter (35) and its support (32). Reconnect the blockage indicator (34).

Final steps
Lift the tractor. Install the wheel. Remove the axle stand and tighten the nuts. Remove the chocks.
Top up the transmission oil level of the rear axle and check it using the gauge located to the rear of the centre housing.
Check the operation of the electrical circuits, the low pressure switch, the solenoid valves, the filter switch and the blockage indicator.
If the pump has been replaced, or if the disassembly of one or several hydraulic component(s) was necessary, check the hydraulic system by carrying out the relevant tests.
Check the tightness of the cover plate mating face, the strainer and the hydraulic unions.

Disassembling and reassembling the high pressure valve

If pressure "P" rises above 200 bar ± 5 bar, the spring (4) is compressed, opening the valve (7) to allow oil to pass into the housing via port R.

Preliminary step
If necessary, take off the right-hand rear wheel. Position a safety stand.

To facilitate valve access, disconnect and plug the linkage valve and spool valve supply hoses.
Unscrew the plug (1). Recover the shims (2) and take out the spring (4).
Remove the "O" ring (5), extract the body (6) with the valve (7) and the washer (8) from the right-hand cover plate. The ball bearing (9) is crimped in the body of the valve.

Check that the valve (7) slides freely in the valve body (6).
Place the washer (8), Install the valve body (6) with the valve (7) into the cover plate. Position the "O" ring (5).
Install the spring (4), the shims (2) and tighten the plug (1) to a torque of 70 - 100 Nm. Reinstall the linkage valve and spool valve hoses.

Reinstall the wheel (if removed). Tighten nuts.