Disassembly and assembly the hydraulic steering unit


If the Orbitrol steering unit is defective, take care that it is replaced with a unit with exactly the same characteristics.
Example: OSPC 150 ON spool valve
OSP = Orbitrol steering pump
C = Valves incorporated in the steering unit
150 = 150 cm3 per rotor revolution
ON = Open centre without feedback

Remove the spool valve from the tractor and tighten it in a clamp with soft jaws.
Remove the jaws if necessary. Take out the screws. Split the manifold from the spool valveCollect the seals.
Take out the screws. Carefully mark the location of the screw and then remove it.
Remove the closing plate, O'ring, stator and O'ring.
Remove the spacer, the rotor, the distributor plate and the O'ring.
Take out the splined link shaft.
Unscrew the threaded ring and take out the valve ball from the non-return valve.
Take out the two pins and valve balls from the suction valves of the steering unit.
Extract the sleeve and spool valve assembly by pushing it out while checking that the pin lies along the horizontal axis.
Remove the washers, the needle bearing and the bush from the sleeve / spool valve assembly. Remove the pin, and the centring springs by pressing on their ends. Separate the sleeve from the spool valve.
Unscrew the plug from the relief valve. Using an 8mm Allen wrench, disassemble the threaded bush and remove the seal, the spring and the valve (the crimped seat cannot be removed).
Unscrew the two plugs from the shock valves. Remove seals. Using a 6mm Allen wrench, remove the threaded bushes and take out the springs, the valve balls and their seats (the crimped seats cannot be removed).
Extract the seal, the bush and the O'ring. Disassemble the non-return valve.
Check and clean the components. Replace any defective parts. Lubricate with clean transmission oil before reassembly.

Reassemble the non-return valve.
Install the seal, the O'ring and the ring.
Place the valve balls and springs in the recesses of the shock valves. Screw on the threaded bushes. Fit the seals and tighten the plugs.
Install the valve and spring in the recesses of the relief valve. Screw in the threaded bush. Fit the seal and tighten the plug to a torque of 40-60 Nm.
Insert the spool valve into the sleeve. Position the centring springs and insert the pin.
Position the bush on the sleeve and spool valve assembly so that the chamfer facilitates assembly in the steering unit.
Place the washers, the chamfer of washer towards the centring springs, by
inserting the needle bearing between them.
Install the sleeve and spool valve assembly in the steering unit by oscillating it slightly. Check that the pin is held horizontally.
Place the two valve balls and the two pins in the recesses of the suction valves.
Install the valve ball in the non-return valve recess. Screw in the threaded bush.
Position the splined link shaft. Install the O'ring and the distributor plate.
Install the rotor so that the two concave depressions lie along the axis of the slot in the splined link shaft. Install the spacer. Place the O'rings on the stator.
While avoiding moving the rotor, fit the stator. Then move it so that its fixing holes match with those of the steering unitInstall the closing plate.

Replace the seals and fit:
- the screw (in the positions marked during disassembly);
- the opposing screws tightened to 30-35 Nm;
- the manifold on the steering unit (screws tightened to 60 Nm);
- the sleeves on the manifold.
Using a test-bench or a suitable fixture, check the adjustment and correct operation of the steering unit. Install the steering unit on the tractor.

Removing and install the steering Ram


The general procedure is similar on fixed or suspended front axles.
Immobilise the tractor. Chock the rear wheels. Apply the handbrake.
To help release the steering ram from its overlap flange, first remove the front left-hand wheel and mudguard (if fitted).
Remove the locknuts and drive ou the steering pivot balls using a suitable extractor tool.
Loosen nut. Remove the right-hand steering link rod (including pivot ball).
Disconnect and block the supply hoses (right and left) from the ram, marking their positioning.
Take out the screws and remove the ram.
Install the steering ram. Tighten the screws to a torque of 120 Nm.
Reconnect the left-hand and right-hand supply hoses of the ram.
Install the link rod and steering pivot balls.
Reassemble the wheel(s). Tighten the nuts and screws to their indicated torque, depending on version.
Adjust wheel alignment. Complete the operation by tightening:
- steering pivot ball nuts  to a torque of 220 Nm;
- steering link rod nuts.

Disassembling and reassembling operations



The steering ram assembly (1) comprises the following parts:
(2) Pack of seals (4) Cylinder (6) Piston pin (7) Cover



Release and remove the ball joints (7).
Separate the cover (7) from the cylinder (4).
Take out the piston (6) from cylinder.
Discard all the seals (sealing ring, O'rings and dust seal).
Ensure that the internal bore of the cylinder and the operational parts of the piston rod are free of scratches: scratches can cause leaks in the steering unit.
Lubricate the seals, bushes and cylinder internal bore with clean transmission oil.
Install the seals on the piston rod (6) cylinder (4) and the cover (7) respectively.

Put together the steering ram without damaging the oil tight seals:
- slide the piston rod fitted with its seals in the cylinder bore;
- put the cover back on the cylinder, with the pressure inlet facing the right direction.
Tighten and lock the ball joints (7) to the torque of 300 Nm.
Install the steering ram on the tractor.
Check the hydraulic pressure on the cylinder line.
Carry out a road test on the steering system.