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Massey Ferguson 8280 Tractor hydrostatic steering for 4WD

The steering system on Massey Ferguson 8280, 8270 tractor is of the dynamic type (constant flowrate of 0.5 l/min, standby pressure of 6 bar). There is no mechanical linkage between the steering wheel and the steering rams. Its control principle is of the Load Sensing type.

The main components of the circuit are:

- pressurised oil feed from the priority block(s) (depending on version) supplied by the variable displacement pump,

- an Orbitrol steering distribution valve of the closed centre OSPD.LS 100 - 260 type with twin stator rotors mounted in by-pass.

- two double acting steering rams connected in parallel and mounted on the 4WD front axles - ZF APL 5052

Fig.36/37. MF 8280, 8270 tractor steering construction (Parts list)

(1) Lip seal, (2) Centring springs, (3) Bush, (4) O’ring, (5) Pin, (6) Sleeve, (7) Spool valve, (8) O’ring, (9) Linkage shaft, (10) O’ring, (11) Plate, (12) O’ring, (13) Plate, (14) O’ring, (15) Spacer, (16) O’ring, (17) O’ring, (18)Integrated spool, (19) Spool body, (20) Seals, (21) O’ring, (22) Washer, (23) Needle bearings, (24) Washer, (25)
Discharge valve, (26) Block, (27) Rotor (100 cm3), (28) Stator (100 cm3), (29) O’ring, (30) Stator (160 cm3), (31) Rotor (160 cm3), (32) Plate, (33) Spring, (34) O’ring, (35) Closing plate, (36) Bolts, (37) Shock valves, (38) Non-return valve, (39) Spacers, (40) One-way valve, (41) Suction valve, (42) Pin

Disassembling and reassembling the distribution valve (Orbitrol)

Disassembly MF 8280, 8270 tractor steering

- Remove the distribution valve from the Massey Ferguson 8280, 8270 tractor.

- Place the distribution valve in a vice fitted with plastic jaw protectors.

- Mark the location of bolts (36). Remove the bolts along with seals (20).

- Take off the closing plate (35), the O’ring (34), the body (19), the integral spool (18) and spring (33).

- Remove the O’ring (17). Locate the position of plate (32) and remove it.

- Remove O’ring (16). Remove stator (30) and rotor (31). Take out the O’ring (14).

- Locate and remove plate (13).

- Remove spacer (15), stator (28), rotor (27). Locate and remove plate (11). Take out O’ring (10).

- Take out the splined linkage shaft (9).

- Unscrew the threaded socket and recover the ball from the non-return valve (38).

- Take out the two pins and the two balls from the Massey Ferguson 8280, 8270 tractor spool valve suction valves (41).

- Extract the sleeve assembly (6) and spool valve (7) by pushing on it and checking that pin (5) lies along the horizontal axis.

- Take out washers (22) (24), the needle bearings (23) and bush (3) from the sleeve / spool valve assembly.

- Take out pin (5) and centring springs (2) by pressing on one of their ends. Separate sleeve (6) from spool valve (7).

- Unscrew the plug of the discharge valve (25). Using an 8 mm Allen key, disassemble the threaded bush and remove the seal, spring and valve (the inserted valve seat cannot be removed).

- Unscrew the two plugs from the shock valves (37), remove the seals. Using a 6 mm Allen key, disassemble the threaded bushes and take out the springs, the balls and their seats (the inserted valve seats cannot be removed).

- Extract the oil tightness seal (1) and O’ring (21).

- Disassemble the check valve (40).

Reassembly MF 8280, 8270 tractor steering

- Check and clean all components, replace any parts found to be defective. Lubricate the components with clean transmission oil before reassembly.

- Refit the check valve (40). Fit seal (1), O’ring (21) and the bush.

- Fit the balls and springs in the housings of the shock valves (37). Screw in the threaded bushes, place the seals and tighten the plugs.

- In the housing of the discharge valve (25), place the valve and spring, screw in the threaded bush. Fit the seal and tighten the plug to a torque of 40 - 60 Nm.

- Introduce the spool valve (6) in sleeve (7). Position the centring springs (2) according to Figure 37 and fit pin (5).

- Position bush (3) on the sleeve and spool valve assembly so that the chamfer facilitates assembly in the spool valve.

- Place washers (22) (24), with the chamfer of washer (24) turned towards the centring springs (2) and placing needle bearing (23) in between them.

- Assemble the sleeve and spool valve assembly in the spool valve using a slight oscillatory movement. Take care that pin (5) is held horizontally.

- In the suction valve housings (41), place the two balls and the two pins.

- In the non-return valve housing (38), place the ball and screw in the threaded bush.

- Position the splined linkage shaft (9). Place the O’ring (10), and the distributor plate (11).

- Fit rotor (27) so that the two cavities "C" lie in the axis of the slot of splined shaft (9). Place the O’rings (12) (29) on the stator (28).

- While avoiding moving the rotor (27), fit the stator (28). Then turn it so that its fixing holes match those in the spool valve.

- Refit rotor (31) on the spacer (15) so that the two cavities "C" lie in the axis of the slot of splined shaft (9).

- Place O’rings (14) (16) on the stator (30). Fit and move it so that the fixing holes match those provided in the spool valve.

- Refit plate (32) in the position noted during disassembly.

- Check that the bore of body (19) and the rim of spool (18) are free of scratches or burs.

- Check that the spool moves normally in the body.

- Slide the spool fitted with its oil tightness components into the body. Place O’rings (17) (34) and spring (33). Refit the closing plate (35).

- Refit the new seals (20) and bolts (36) at the emplacement noted during disassembly.

- Alternately tighten the bolts to a torque of 30 - 35 Nm.

- Using a test bench or an appropriate fixture, check the adjustment and operation of the spool valve. Refit the spool valve on the tractor.

- Check the oil tightness of the unions.

Fig.58. Layout of channels and ports

Disassembling and reassembling Massey Ferguson MF 8270, 8280 tractor steering ram

Removal

Fig. 55

- Disconnect the hoses (2), carefully noting their positions (Fig. 55-56)

- Loosen and take off nut (4) holding cylinder (3) on the stub (7) concerned.

- Repeat the previous operation with the fixing point of the piston rod.

- Remove washers (6), spacers (1), carefully noting their positions.

- Remove the ram(s) (1).

- If necessary, take out the circlip(s), remove the ball joint(s) (8).

Refitting

Fig. 56

- If removed, replace the ball joint(s). Fit the circlip(s). (Fig. 56)

- Refit the ram(s), spacer(s) (1) with the chamfer facing the ball joint and washers (6).

- Fit and tighten the nut(s) (4) to a torque of 440 Nm. Reconnect the hose pipes (2).

- Using a grease gun and bearing grease, grease the pins (7).

Disassembly

- Take off snap ring (14) by turning the oil tight stuffing box (5) using a locally manufactured pin wrench. Take out piston rod (15) from cylinder (3).(Fig. 57)

- Fix the piston rod in a vice using the end intended for holding the ball joint.

- Loosen and remove nut (2).

- Remove piston (4) and take off O’ring (9).

- Separate the stuffing box (5) from the shaft (15).

Remove:

- from the piston: oil seal (6), bush (7) and O’ring (8).
- from the oil tight stuffing box: O’ring (10), washer (11), oil seal (12), oil scraper seal (13).

Fig. 57

Reassembly

- Clean and inspect the components. Replace any found to be defective.(Fig. 57)

- Check that the bore of the cylinder (3) and the rim of the piston (4) are free from scratches and that the oil passage ports in the cylinder are not blocked.

- Carefully refit - on the stuffing box (5): oil seal (12), scraper seal (13), washer (11) and O’ring (10).

- Lubricate the oil seals, O’rings and oil scraper seal.

- Slide the stuffing box in the correct direction on to the shaft (15) (Fig. 12).

- Refit with care - on piston (4): O’ring (8), bush (7) and oil seal (6).

- Place a lubricated O’ring (9) against the shoulder of the shaft (15).

- Slide the piston in the correct direction on to the screw cut end of shaft (15).

- Carry out operation 56 again to grip the piston rod.

- Discard the used nut (2). Fit and tighten a new nut to a torque of 405 Nm.

- Lubricate the bush (7) and the oil seal (6).

- Slide the shaft assembly (15), stuffing box (5) and piston (4) into cylinder (3).

- Position the machined groove of the stuffing box opposite that of the cylinder.

- Fit snap ring (14) using the same method as in operation 55.

- Refit the ram(s) on to the tractor.

- Check the operation and the internal oil tightness of the ram(s).