Open centre hydraulic system (57 l/min)


The open centre hydraulic system comprises two separate systems.


These two systems are supplied by a two-stage gear pump (1) fitted on the internal face of the right-hand hydraulic cover plate. The pump sucks transmission oil from the common tank formed by the centre housing and the gearbox through a 150 micron filter (1), also fitted on the right-hand cover
plate. 


A 15 micron main filter (39) and a blockage indicator (40) are fitted to the low flow rate system upstream of the Orbitrol steering spool valve. The hydraulic pump is driven by the ring gear of the PTO clutch unit.

Low-pressure system, low flow rate

The first stage of the pump supplies the hydrostatic steering where pressure can reach 170 bar.


Hydraulic flow
After supplying the Orbitrol steering spool valve as required, the oil is directed to the left-hand cover plate attached to the centre housing. This cover plate performs several low-pressure functions. It ensures:
- operating pressure for the various transmission components via a 17 bar valve (2) fitted downstream from the Orbitrol unit;
- cooling and lubrication of the gearbox and connected components,
- pressure for the brake master cylinders (excluding MERITOR master cylinders).

Tractor transmission components
The 17-bar system supplies, in parallel, the various transmission functions via solenoid valves flanged on the reverse shuttle clutch unit, on the Speedshift control and in the main channel of the right-hand cover plate. None of these functions has priority and they may be activated simultaneously. Some of the solenoid valves (4WD, power take-off, Speedshift and reverse shuttle (proportional solenoid valves)) are linked to the tractor's electronic system. The functions supplied by the low flow rate system are as follows:
- the hydrostatic steering,
- the Hare / Tortoise range shifting (Hi / Lo),
- the differential lock (front and rear),
- the 4WD clutch,
- the Speedshift,
- The clutch control valve,
- the clutch unit of the reverse shuttle,
- the power take-off system,
- clutch,
- brake,
- front PTO (depending on option).

Cooling and lubrication
When the various components of the transmission are supplied, the left-hand cover plate directs oil towards the cooler when it is hot, or directly towards to the gearbox and PTO when it is cold. The lubrication pressure is maintained by a valve (10) set to 1.5 bar and fitted on the front left-hand side of the gearbox.


Pressure for brake master cylinder
Only unassisted master cylinders receive pressure from the hose (1) connected upstream to the 1.5 bar valve (10).

Layout of the main Speedshift and Power Shuttle system components

Parts list
(1) Front differential lock (2) Steering ram (3) Pressure connector (4) Hydrostatic spool valve (Orbitrol)
(5) Forward clutch (reverse shuttle) (6) Reverse clutch (reverse shuttle) (7) Accumulator (assisted master cylinders) (8) Speedshift mechanism (9) Left-hand cover plate (10) 1.5 bar valve (11) Temperature switch
(12) Hare/Tortoise mechanism (13) PTO clutch (14) Pump suction pipe (16) Restrictor (17) Suction strainer (Reverse shuttle clutch lubrication pump) (18) 4WD clutch (19) Brake lubrication pipes (20) Rear differential lock (23) Oil cooler (24) Brake master cylinders (25) FTE valve
(26) Bleed connector (27) Diagnostics connector (reverse shuttle lubrication)
(28) Proportional solenoid valves (reverse shuttle) (30) Speedshift solenoid valve (31) Gearbox control unit (32) Accumulator (33) 60 micron filter (34) Hare/Tortoise solenoid valve (35) Differential lock solenoid valve (36) PTO solenoid valve (37) PTO brake solenoid valve (38) 4WD solenoid valve (39) 15 micron filters (40) Blockage indicator (43) Two-stage hydraulic pump (44) 150 micron suction filter (45) Left and right brakes (47) PTO brake

Layout of the main Speedshift and mechanical reverse shuttle system components

Parts list 
(15) Linkage valve (21) Auxiliary spool valves (22) Lift rams (41) Trailer brake valve (spool valve) (42) High pressure safety valve (46) Trailer brake connector (49) 1.5 bar valve (clutch(es) lubrication system) (50) Hydraulically controlled clutch master cylinder (61) Speedshift mechanism
(62) Speedshift solenoid valve

High-pressure system, high flow rate

The second stage of the pump supplies, in the following order:
- the trailer brake spool valve, which is priority (if fitted);
- the auxiliary spool valves;
- the linkage valve.
The oil not used by the trailer brake spool valve supplies the auxiliary spool valves fitted to the rear of the linkage cover plate. Starting at the auxiliary spool valves, a line supplies the linkage spool valve located on the left-hand side cover plate. The excess flow rate from the spool valves returns to the pump suction manifold via a restrictor (16) without passing through the 150 micron filter. A safety valve, set to 200 bar, is fitted in the discharge channel on the right-hand cover plate to protect the high pressure system.

Mechanical reverse shuttle and Speedshift diagram 

Parts list
(1) Front differential lock (2) Steering ram (3) Pressure connector (approximately 5 bar) (4) Hydrostatic spool valve (Orbitrol) (5) Forward clutch (Power Shuttle) (6) Reverse clutch (Power Shuttle) (8) Speedshift mechanism (9) Gearbox (10) 1.5 bar valve (11) Temperature switch
(12) Hare/Tortoise mechanism (13) PTO clutch (14) Pump suction pipe (15) Linkage spool valve (16) Restrictor (18) 4WD clutch (19) Brake lubrication pipes (20) Rear differential lock (21) Auxiliary spool valves (22) Lift rams (23) Oil cooler (24) Brake master cylinders
(25) Tank (excluding MERITOR master cylinders) (26) Connector to assist brake bleeding (28) Proportional solenoid valves (Power Shuttle) (31) Clutch unit (reverse shuttle) (32) Accumulator
(33) 60 micron filter (34) Hare/Tortoise solenoid valve (35) Differential lock solenoid valve (36) PTO solenoid valve (37) PTO brake solenoid valve (38) 4WD solenoid valve (39) 15 micron filters
(40) Blockage indicator (41) Trailer brake valve (spool valve) (42) High pressure safety valve (43) Two-stage hydraulic pump (44) 150 micron suction filter (45) Left and right brakes (46) Trailer brake connector (47) PTO brake (48) Valve (reverse shuttle, reverse clutch, opening at 13 bar) (49) 1.5 bar valve (clutch(es) lubrication system) (50) Left-hand hydraulic cover plate
(61) Speedshift mechanism (62) Speedshift solenoid valve (63) Front PTO solenoid valve (64) Clutch thrust bearing (65) Assisted clutch master cylinder  (66) Non-return valve (clutch control) (67) Accumulator

Reverse shuttle 

Lubrication

(5) To forward clutch lubrication (6) To reverse clutch lubrication (7) Lubrication pump (17) Suction strainer (27) Diagnostics connector (49) 1.5 bar valve

Power Shuttle and Speedshift diagram 

Parts list
(1) Front differential lock (2) Steering ram (3) Pressure connector (approximately 5 bar) (4) Hydrostatic spool valve (Orbitrol) (5) Forward clutch (Power Shuttle) (6) Reverse clutch (Power Shuttle) (8) Speedshift mechanism (9) Gearbox (10) 1.5 bar valve (11) Temperature switch
(12) Hare/Tortoise mechanism (13) PTO clutch (14) Pump suction pipe (15) Linkage spool valve (16) Restrictor (18) 4WD clutch (19) Brake lubrication pipes (20) Rear differential lock (21) Auxiliary spool valves (22) Lift rams (23) Oil cooler (24) Brake master cylinders (25) Tank (excluding MERITOR master cylinders) (26) Connector to assist brake bleeding
(28) Proportional solenoid valves (Power Shuttle) (31) Clutch unit (reverse shuttle) (32) Accumulator (33) 60 micron filter (34) Hare/Tortoise solenoid valve (35) Differential lock solenoid valve
(36) PTO solenoid valve (37) PTO brake solenoid valve (38) 4WD solenoid valve (39) 15 micron filters (40) Blockage indicator (41) Trailer brake valve (spool valve) (42) High pressure safety valve
(43) Two-stage hydraulic pump (44) 150 micron suction filter (45) Left and right brakes (46) Trailer brake connector (47) PTO brake
(48) Valve (reverse shuttle, reverse clutch, opening at 13 bar) (49) 1.5 bar valve (clutch(es) lubrication system) (50) Left-hand hydraulic cover plate (61) Speedshift mechanism (62) Speedshift solenoid valve (63) Front PTO solenoid valve