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Massey Ferguson 8250, 8240 Powershift gearbox - Creeper

MF 8100-8200 Series Tractors Repair Operations

MF 8250, 8240 Tractors fitted with an AG150 or AG250 Powershift gearbox may be fitted, according to options, with a creeper. This reducer unit (24) comprises a simple epicyclical gear train having a planetary carrier and crownwheel mounted at the front of the intermediate housing (19).

It is controlled by a lever on the right-hand side console in the cab that is linked via a cable to a link fitted on the front right-hand side of the intermediate housing. This link moves the coupler control fork. The coupler, fitted with straight teeth, must only be engaged when the tractor is stationary.

Operation

The coupler (29) is integral via splines with the layshaft (30). The moving of the control lever to the "Snail" position moves the coupler rearwards and locks it to the planetary carrier (20) via coupler ring (22). The speed of the output shaft is 1/4 of that of the input shaft.

Lubrication

The lubrication of the mechanical components of the epicyclical reducer gear is ensured by an oil splash. The drive pinion and the layshaft (30) have an axial drilled channel, this allows flow "D" from the right-hand side hydraulic cover to lubricate needle bearing (34).

The bearing supports the layshaft and permits a difference in rotation of the shafts when in the "Creeper" position.

(1) Snap ring (2) Connecting shaft (3) Bolts (4) Sleeve (5) Support (6) Snap ring (7) Bearing carrier (8) Circlip (9) Circlip (10) Ball bearing (11) Snap ring (12) Friction washer (13) Pin (14) Friction plates (15) Sun gears (16) Crownwheel (17) Spacers (18) Roller bearings (19) Intermediate housing (20) Planetary carrier (21) Snap ring (22) Coupler ring (23) Bolts (24) Planetary carrier assembly (reducer gear) (25) Locating pin (26) Nut (27) Fork (28) Guide rod (29) Coupler (30) Layshaft (31) Snap ring (32) Sleeve (33) Snap ring (34) Needle bearing (35) Locking stud (36) Spring (37) Plug (38) Pin (39) Finger (40) O’ring (41) Pin (42) Link (43) Bolt (44) Housing (45) Shim(s)

Removing and refitting the unit

Uncouple the Massey Ferguson 8250, 8240 tractor between the gearbox and the intermediate housing. Remove the sleeve (4). Remove bolts (3). Remove the shaft (2) and unit (24) assembly.

The locating pins (25) are force fitted into the intermediate housing (19). Check for the presence of the locating pins on the intermediate housing. Screw two guide studs of suitable length in the place of two bolts (3).

Place coupler (29) in contact with snap ring (31). Refit shaft (2) and unit (24) assembly turning the machined recess "E" on support (5) towards the adjusting nut (26) on guide rod (28).

Turn shaft (2) several turns to engage the exterior splines of coupler ring (22) in those of coupler (29). Alternately and uniformly tighten bolts (3) lightly smeared with Loctite 241 to a torque of 90 - 120 Nm. Couple the tractor between the gearbox and the intermediate housing.

Disassembling, reassembling and adjusting the selection mechanism

Remove unit (24). Disconnect the control cable fitted to link (42).

Disassembly

Remove plug (37). Recover spring (36) and locking stud (35). Remove the Allen screw (43). Remove the link (42) and pin (41) fitted with seal (40) and finger (39). Recover the shim(s) (45).

Drive out pin (38) linking the pin and the finger. Disengage the guide rod (28) from the fork (27) and the intermediate housing (19). If necessary, loosen, unscrew and discard nut (26). Remove the fork, coupler and shaft (30) fitted with needle bearing (34).

Remove snap ring (31). If necessary, extract the bearing. Clean and check the components. Replace any parts found to be defective.

If fitted, using an appropriate fixture, insert bearing (34) thrust against the shoulder on layshaft (30) and check that the needle bearing turns normally. Place snap ring (31). Lubricate a new seal (40) and fit it on pin (41).

Enter the pin through the chamfered port of the intermediate housing (19). To limit axial clearance of the pin, it is recommended to carry out shimming with a tolerance of 0.1 mm to 0.6 mm.

Shimming

- On the pin, place an approximate thickness of shim(s) (45). Fit finger (39) and partially fit pin (39). Reassemble the link (42) and bolt (43).

- Manually evaluate the existing clearance.

- The adjustment principle consists in obtaining a minimum clearance between the various parts.

Action - If the clearance is outside the maximum stated tolerance, determine a new thickness of shim(s). After shimming, check for the correct orientation of the finger and the link.

Definitively insert pin (38), fit and tighten Allen screw (43). Fit the shaft, coupler and fork in the intermediate housing. Refit the guide rod and nut assembly. Refit the unit (24). Adjust the fork.

Couple the MF 8250, 8240 tractor between the gearbox and the intermediate housing. Connect the control cable and adjust it if necessary.

Adjustment

- Fit the locking stud (35), spring (36) and plug (38). Partially tighten the plug.
- Position coupler (29) in accordance with F1, its forward face thrust against shaft (2).
- Maintain the fork thrust against the coupler in accordance with F2. Turn the guide rod (28) in nut (25) according to F3 so as to place in contact the oblique face of groove G1 with locking stud (35) while simultaneously holding nut (26) against spot-faced face B of the intermediate housing (19).
- Using a depth gauge, measure X1 between the forward face of the guide rod and face A of the intermediate housing (19).
- Hold the fork thrust against the coupler in accordance with F2.
- Turn the guide rod in the nut in accordance with F4 so as to place the other oblique face of groove G1 in contact with the locking stud while holding nut (26) as previously.
- Measure X2 in the same manner as X1.
- Determine the position of adjustment X using the following formula: X = (X1 + X2) : 2
- Provisionally position guide rod (28) to dimension X.
- Place coupler (29) in the "Creeper unit" position. Manually check for locking of the control and the clearance between the fork and the coupler.
- If this check is satisfactory, remove unit (24), plug (37), the spring and the locking stud.
- Grease the threads of the guide rod and the threads of nut (26).
- Tighten the nut, previously lightly smeared with Loctite frein filet faibe, and definitively position the guide rod according to the previously calculated dimension X.
- Lock the nut by bending its collar into the machined groove of the guide rod.
- Reassemble the locking mechanism. Tighten plug (37) to a torque of 50 - 70 Nm. Refit unit (24).

Disassembling and reassembling the epicyclical reducer gear

Remove unit (24). Take out bolts (23). Remove housing (44). Disengage reducer gear (20) from shaft (2). Remove crownwheel (16). Separate supports (5) (7). If necessary, take off snap ring (6) and circlips (8) (9).

Extract bearing (10). Remove the friction washers (12). Take off circlip (11). Drive out pins (13). Remove sun gears (15) taking care not to lose the needle bearings (18), spacers (17) and the friction plates (14).

The coupler ring (22) is fitted in the planetary carrier using a press. Snap ring (21) provides additional locking of the various parts.Check and clean the components. Replace any parts found to be defective.

Fit each sun gear (15) with both needle bearings (18) and spacer (17) smeared with miscible grease. Refit the sun gears and position the friction plates (14).

Refit pins (13) correctly turning the spot-face for the fitting of snap ring (11). Fit the snap ring. Manually check the axial clearance and rotation of each sun gear.

Lightly smear the faces of the reducer gear with miscible grease and fit the friction washers (12), with the tabs lodged in the appropriate grooves. If disassembled, insert bearing (10) on shaft (2) using an appropriate fixture.

Fit circlips (8) (9) and snap ring (6). Assemble supports (5) (7). Engage reducer gear (20) on shaft (2). Refit the
crownwheel (16).

Position housing (44), with the cut out turned downward. Assemble and tighten bolts (23) previously lightly smeared with Loctite 241 and tighten to a torque of 10 - 14 Nm. Refit unit (24).

Adjusting the control

On lever "A"

Place control lever "A" in the "Snail" position. Screw yoke (1) flush with the end of the threaded part of the cable (6). Fit the yoke (1) on to lever "A" with clip (7).

Tighten nut (2). Tighten nut (3) against sheath end (5). Fit the sheath end and Grower washer on to the support. Tighten nut (4) checking that the cable is not pinched.

On link "B"

Place link "B" in the "Creeper" position (coupler (29) locked by splines to planetary carrier (20) fork locked). Screw yoke (9) flush with the threaded part of cable (6).

Assemble yoke (9) on to link "B" using clip (10). Tighten nut (11). Adjust stop (12) using nut (13) on support (8) while checking that link "B" is still correctly locked.