Removing and install the right-hand hydraulic cover plate


Immobilise the tractor. Chock the left rear wheel.
If the tractor is not equipped with a Park Lock device, engage the hand brake.
Chock between the frame and the front axle (optional).
Partially drain the intermediate housing (GPA30 rear axle) or the centre housing (GPA20 and GPA40 rear axles).
Remove the rear right-hand wheel. Place a safety stand under the trumpet housing. Mark and disconnect the pipes or hoses, the solenoid valve harnesses (depending on version), switches and the engine speed sensor connected to the hydraulic cover plate (8).
Remove the 60 μ filter (49) (GPA30, GPA40 rear axles).


Unscrew:
- the screws (32). Remove the main filter assembly (27);
- the screws (4). Remove the single priority block (B) or the hydraulic unit with two priority blocks (A+B). In order to avoid draining the trailer brake system on tractors fitted with a two-priority block hydraulic unit, it is recommended to remove the complete unit from the hydraulic cover plate without disconnecting the control hose (22) from the brake master cylinders (40 kph tractors) or from the block/valve assembly (tractors fitted with high-pressure braking).
Unscrew the screws (1). Release and remove the hydraulic cover plate.
Remove the seal (4). Discard this seal.


If necessary, remove the safety valve (45) from the low pressure system by proceeding as follows:
- Compress the spring (3) using a screwdriver.
- Remove the circlip (1).
- Remove the components (2) to (4).


If necessary, unscrew the castellated collar (2) (GPA40) using pin wrench 3378466M1. If necessary, discard and replace the "O" ring (1).



Reinstall
Clean the mating face of the intermediate housing (GPA30) or centre housing (GPA20 and GPA40) and the mating face of the right-hand hydraulic cover plate. If necessary, screw on and tighten the castellated collar (2) using the pinIf necessary, reinstall the safety valve (45).
Check that the component (4) slides freely in its housing after reinstalling.


Check the hydraulic cover plate for presence of:
- the locating pins (36);
- the rivets obstructing the end of the hydraulic channels of the hydraulic cover plate faces (external and internal).


For GPA30, if necessary:
- position the pipe of the 5 bar safety valve in the intermediate housing by placing its end, Installed with a seal, in the Mecanindus pin. This pin is located on partition C of the intermediate housing;
- Install the charge pipe (54) fitted with an "O" ring (52) in the intermediate housing by placing the pipe notch in the pin (1).


Lightly smear the seal (4) with miscible grease. Position this seal:
- on the collar of the pipe (54) (GPA30);
- on the castellated collar (2) screwed onto the pipe (3) (GPA40).
Lightly smear the mating face of the intermediate housing (GPA30) or centre housing (GPA20 and GPA40) with a sealing product such as Loctite 5206 or equivalent. For the GPA20 and GPA40 rear axles, do not obstruct the PTO hydraulic port.
If necessary, screw on two diametrically opposed guide studs (G) onto the intermediate housing (GPA30) or centre housing (GPA20 and GPA40).
Fill the variable displacement pump (41) with clean transmission oil through port O.


Slide the cover plate onto the guide studs (G) previously screwed onto the intermediate housing (GPA30) or centre housing (GPA20 and GPA40). Using a bronze hammer, gently tap the rim of the hydraulic cover plate (8) to begin engagement of the locating pins (36) in the intermediate or centre
housing. When fitting the hydraulic cover plate to the intermediate or centre housing, check between the mating faces (cover plate and housing) to ensure that the continuity pipe (1) (GPA20 and GPA40) or (55) (GPA30) is correctly fitted in the 5 bar safety valve (44) as per the GPA40 example.


Screw in the screws (1) and simultaneously remove guide studs G (if used). Tighten these screws to a torque of 120-160 Nm. If resistance is felt during tightening, do not continue. Move aside the hydraulic cover plate for the intermediate housing (GPA30) or centre housing (GPA20 and GPA40) and check that the continuity pipe or (55) is fitted in the 5 bar safety valve. Also turn the driven gear (39) of the variable displacement pump to assist with gear engaging.


Replace the "O" rings (1) to (3) for the single priority block (7) (tractors without trailer braking) or for the hydraulic unit with two priority blocks [(7) and (10)] (tractors with trailer braking).


Reinstall the single priority block or the hydraulic unit with two priority blocks (7) or [(7) and (10)]. Lightly smear the thread of the screws with Loctite 542 or equivalent. Tighten these screws to a torque of 25 - 35 Nm.


For tractors fitted with a GPA30 rear axle and a trailer brake mechanism:
- Tighten the T connector (1) in the vertical position. Never replace the T connector (1) with a standard plug.
- Tighten the hose (13).
- Temporarily tighten the hose (50) while awaiting the filling operation.


For tractors fitted with a GPA20 or GPA40 rear axle and a trailer brake mechanism:
- Tighten the elbow union (1). Never replace the elbow union 1) with a standard plug.
- Tighten the pipe or hose (13) (depending on version).
If necessary, adjust the engine speed sensor located on the hydraulic cover plate. Reconnect:
- the switches;
- the solenoid valve harnesses;
- the pipes and hoses.
Top up the rear axle oil level. Check using the dipstick or the sight glass (depending on version).

For tractors equipped with a GPA30 rear axle and a trailer brake mechanism:
- Charge the hose (50) for the priority block (10).
- Definitively tighten the hose (50).
If the variable displacement pump had to be replaced, perform the hydraulic tests. Lift the right-hand side of the tractor rear axle. Reinstall the wheel. Remove the axle stand. Tighten the wheel nuts.
Check for correct operation:
- of the electrical and electronic circuits;
- of the switches;
- of the solenoid valves.
Carry out a road test.
Check tightness of:
- the right-hand hydraulic cover plate;
- the mating faces;
- Hydraulic unions