Hydraulic system - Right-hand cover plate


The right-hand cover plate is fitted on the intermediate housing (GPA30 rear axle) or the centre housing (GPA20 and GPA40 rear axles). It is the main support for a number of components. It incorporates the various channels for the charge system, the lubrication system and the low flow rate and high flow rate systems of the 110 l/min or 150 l/min Load Sensing system.


 On its internal face, the cover contains:
- the variable displacement pump (41) with a capacity of 45 cm3/revolution (GPA20, GPA30 and GPA 40 rear axles) (110 l/min Load Sensing hydraulic system) or the variable displacement pump (41) with a capacity of 60 cm3/revolution (GPA 40) 150 l/min Load Sensing hydraulic system)
- its drive gear (39) fitted to the variable displacement pump
- the safety valve (45) of the low pressure system set to 24 bar,
- the safety valve (44) of the charge and lubrication system set to 5 bar. This safety valve differs depending on the tractor's Load Sensing hydraulic equipment (110 l/min or 150 l/min).


On its external face, the cover contains:
- the main filter 15 μ (27); this differs depending on the tractor's Load Sensing hydraulic equipment (110 l/min or 150 l/min).
- one or two priority blocks serving different functions of the low and high flow rate systems.
For the 40 kph version with trailer braking, the tractors are fitted with a hydraulic unit with two priority blocks. For the 50 kph version with or without trailer braking, the tractors are systematically fitted with a hydraulic unit with two priority blocks. These priority blocks can be distinguished from the priority blocks on the 40 kph version with trailer braking by a higher number of hydraulic ports. 
These additional hydraulic ports are used by the high-pressure braking unit;
- the pressure relief-valve (2);
- the variable displacement pump hydraulic regulator (12);
- the three or four flanged solenoid valves (2 or 4WD) that control the low pressure functions (17 or 21 bar);
- diagnostics connectors for high and low pressure (11) (20), lubrication charge (29), LS (9);
- the engine speed sensor (25) (if fitted);
- the low pressure (14) and charge (42) switches as well as the main filter blockage indicator (34).


Description
The engine movement transmitted to the gear (1) via the shaft (2) drives the gear (39) of the variable displacement pump (41). The shaft (2) is splined to the engine flywheel vibration damper via the PTO shaft. The oil coming from the charge pump located on the left-hand cover plate (see chapter 9) is directed towards the priority block via the pipe (3) (GPA20 and GPA40) or the pipe (54) (GPA30) via the variable displacement pump (41), to supply the required function.
The pipe (1) (GPA20 and GPA40 rear axles) or the pipe (55) (GPA30 rear axle) carries the oil coming from the 5 bar safety valve (44) to the suction manifold (4) fitted on the left-hand cover plate.

GPA20 and GPA40 rear axles assemblies 


GPA20 LS 110 l/min
GPA40 LS 110 l/min
GPA40 LS 150 l/min


Parts list
(1) Continuity pipe from safety valve (44)  (2) Charge pump (3) Charge pipe (4) Suction manifold (41) Variable displacement pump (44) 5 bar safety valve


Legend
A Source of suction

GPA30 rear axle assembly

GPA30 LS110 l/min


Parts list
(2) Charge pump (4) Suction manifold (22) Mecanindus pin (41) Variable displacement pump (44) 5 bar safety valve (52) "O" ring (53) "O" ring (54) Charge pipe (55) Continuity pipe linked to the 5 bar valve

Legend
A Source of suction
C Compartment


Parts list 
(1) Screw (2) High-pressure (HP) relief valve (3) Supply to the Orbitrol spool valve (4) Screw (5) LS pilot flow from the Orbitrol spool valve (6) LS pilot flow to the variable displacement pump hydraulic regulator (7) Single priority block (40 kph tractors without trailer braking) (8) Hydraulic cover plate (9) LS diagnostics connector (10) Hydraulic unit with two priority blocks (40 kph
tractors with trailer braking) (if fitted) (11) High-pressure (HP) diagnostics connector (12) Pump hydraulic regulator (13) Trailer brake unit vent line (14) Low pressure (BP) switch (17 or 21 bar) (15) to (18) Solenoid valves (PTO, PTO brake, front and rear differential lock, 4WD (if fitted))
(19) Flanges (20) Low-pressure (BP) diagnostics connector (17 or 21 bar) (21) PTO pipe (22) Trailer brake control from brake master cylinders (40 kph tractors) or block/valve assembly (tractors fitted with high-pressure braking) (23) PTO brake pipes (24) 2WD or 4WD differential lock pipes
(25) Engine speed sensor (if fitted) (26) 4WD pipes (27) Main filter (15 μ) (28) Hydraulic line (17 or 21 bar) (29) Lubrication and charge pressure diagnostics connector (30) Supply to the linkage valve and auxiliary spool valves (31) LS pilot flow from auxiliary spool valves and linkage valve (32) Screw
(33) Hydraulic line supply to trailer brake rear coupler (34) Blockage indicator (there are two types of fitting, depending on tractor serial number) (35) Screw (36) Locating pins (37) Nut (38) Washer (39) Gear (40) Key (41) Variable displacement pump (42) Lubrication and charge pressure switch
(43) Hydraulic lines (running to and from the cooler) (44) 5 bar safety valve (45) 22 or 24 bar safety valve (46) Temperature switch or plug and "O" ring (there are two types of fitting depending on tractor serial number) (47) Variable displacement pump screw (48) Hydraulic lubrication line (49) 60 micron filter element (50) Charge hose (GTA1040) (51) Screw

Legend
A Single priority block (40 kph tractors without trailer braking)
TR16 Connector
TR17 Connector


In addition to the assembly views, the figure also shows hydraulic components C1, C2 or C3, which may be fitted on or around the LS right-hand hydraulic cover plate depending on the tractor hydraulic update
level and the type of rear axle (GPA20, GPA30 or GPA40).


Identification of channels and ports

on the hydraulic regulator (12) 


C 22 bar adjustment screw
D 200 bar adjustment screw
P High pressure (HP) from variable displacement pump
R To variable displacement pump control piston
S Hydraulic regulator return
(8) Hydraulic cover plate
(9) LS diagnostics connector
Screws C and D are factory set. Do not modify these settings.

on the hydraulic cover plate (8) and the variable displacement pump (41) 


F To main filter (15 μ)
G Charge line
L Lubrication line
P High pressure (HP) outlet from variable displacement pump
PTO supply line (GPA20 and GPA40)


R Line to variable displacement pump control piston
S Hydraulic regulator return line
S1 Priority block(s) return line (depending on version)
(2) 230 bar high-pressure (HP) relief valve
(11) High pressure diagnostics connector
(29) Lubrication and charge pressure diagnostics connector
(44) 5 bar safety valve
(45) 22 or 24 bar safety valve