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Massey Ferguson 8280 gearbox with Power Shuttle – Mainshaft

MF 8100-8200 Series Tractors Repair Operations

The mainshaft (7) fitted to MF 8280 heavy gearboxes with a power shuttle rotates on two taper roller bearings (9) (10) and (20) (21) lying in the two lower bearing blocks of the main gearbox.

The input pinion (1), fitted at the front, is integral with the shaft via splines. It is held by washer (2) and nut (3).

Between the two lower bearing blocks, the shaft holds the driving pinions of 2nd (13) and 1st (19) that run free, as well as the synchromesh assembly for 1st and 2nd, the hub of which is splined to the shaft.

At the rear the shaft holds the 4th gear driving pinion (24) that runs free and the synchromesh assembly for 3rd and 4th gear. The synchromesh is of the double cone type.

The rear bore receives bearing cup (22) of the taper roller bearing of the output shaft. The lubrication of the 1st gear
pinion and 2nd gear bush is ensured by a central channel with radial ports.

The pre-loading of bearings is adjusted by means of shim(s) (11) placed behind bearing cup (10).

(1) Input pinion (2) Tab washer (3) Nut (4) Lubricating pipe (5) Snap ring (6) Spring (7) Mainshaft (8) Bush (9) Bearing cone (10) Bearing cup (11) Shim(s) (12) Spacer (13) 2nd gear driving pinion (14) 2nd gear synchromesh cone (16) 1st and 2nd gear synchromesh (18) 1st gear synchromesh cone (19) 1st gear driving pinion (20) Bearing cone (21) Bearing cup (22) Bearing cup (24) 4th gear driving pinion (25) 4th gear synchromesh cone (27) 3rd and 4th gear synchromesh (29) Snap ring (32) 3rd gear synchromesh cone.

To take out the mainshaft, it is necessary to remove the gearbox.
Uncouple the Massey Ferguson 8280 tractor between the gearbox and the intermediate housing.
Separate the gearbox from the engine. Remove the selector cover. Place the gearbox on a suitable fixture.
Take off the input unit. Remove the selector rails and forks. Remove the output shaft.

Disassembling and reassembling the shaft

To remove the synchromesh (27) and 4th gear driving pinion (24), it is necessary to remove circlip (56) from the machined groove of layshaft (51). Then, push back the pinion (57).

Take off snap ring (29). Remove the 3rd and 4th gear synchromesh (27), carefully marking its position. Remove the synchromesh parts (rings, cones and bushes) carefully marking their locations if the pinion (24) is to be reused later. Immobilise the shaft using a locally made tool using a MF 8280 4 WD clutch plate.

If necessary, remove lubricating pipe (4) and spring (6). Completely unscrew nut (3) (60 mm flat) using socket.
Remove tab washer (2) and the input pinion (1). Take out bush (8) complete with bearing cone (9).

Remove the tool. Take the shaft out of the housing complete with the 1st gear driving pinion (19) towards the rear via the bearing block opening, while holding together the 1st and 2nd synchromesh, pinion and fork assembly.

The extraction of the 1st and 2nd gear fork from the housing is carried out along with the synchromesh assembly (16) and the 2nd gear driving pinion (13).

Remove the complete assembly (synchromesh, 2nd gear pinion and fork) through the selector cover opening. Take out bearing cups (10) (21). Carefully match the cups and cones if they are to be re-used.

Remove the shim(s) (11) and spacer (12). If necessary, extract bearing cones (9) (20) and bearing cup (22). Take off snap ring (5). Clean and check the parts, discard any defective ones.

Ensure that the central and radial lubricating channels of shaft (7) are not blocked. If removed, using a press and a suitable fixture, insert the bearing cones (9) (20) on bush (8) and shaft (7). On the latter, also position snap ring (5) and insert cup (22).

Lubricate the bearing cups and cones. Install bearing cup (21). Check for wear on synchromesh parts of 1st and 2nd gear. Outside the housing, assemble the 2nd gear pinion (13), new synchromesh parts and 1st and 2nd gear synchromesh.

If the synchromesh parts are to be re-used, refit each part in its initial position, as marked during disassembly.
Between the two compartments, refit the complete assembly with the 1st and 2nd gear fork correctly positioned.

Slide the shaft and 1st gear pinion (19) through the rear of the housing while holding the pinion / synchromesh assembly. Shim the shaft. Install pinion (1). Degrease the threaded end of the shaft using solvent.

Hold the shaft as desribed in operation. Clean and lightly smear the new nut (3) with Loctite 270 or equivalent then tighten it to a torque of 130 - 170 Nm using the socket previously used.

Lock the nut by bending its collar, without breaking it, into the grooves of the shaft using a suitable drift. Manually check the rotation of the shaft. If removed, fit spring (6) and lubricating pipe (4) in shaft (7).

Check the wear of the 3rd and 4th gear synchromesh parts. Install the synchromesh parts that are being re-used, according to the markings made during disassembly.

Position the driving pinion of 4th gear (24) and the synchromesh of 3rd - 4th (27). Move forward pinion (57) on the mainshaft. Install circlip (56) in its throat without bending it, and ensuring that it is correctly positioned. Place snap ring (29).

Manually check:

- the axial clearance of the pinions
- the rotation of the shaft and its pinions.

Reassemble the output shaft. Install the input unit. Reassemble the selector rails. Adjust the 1st - 2nd and Hare / Tortoise forks and selectors.

Install the selector cover. Check that the gear shifting operates correctly and also check for the presence of the Hare / Tortoise position. Connect the gearbox with the engine.

Couple the Massey Ferguson 8280 tractor to the gearbox and the intermediate housing. Check the oil tightness of mating faces and hydraulic unions. Carry out a road test of the Power Shuttle, gears, Hare / Tortoise range and A, B, C and D ratios of the Dynashift.

Shimming the shaft

Determine the thickness of shim(s) (11) required to obtain a provisional clearance of 0.10 to 0.15 mm for the later loading of the bearings.

Reminder: It is essential to place spacer (12) against the housing, the previously determined shim(s) (11) and bearing cup (10).

Slide bush (8) fitted with cone (9) and pinion (1) onto shaft (7). Install washer (2) and nut (3). Place the locking tool on the shaft, tighten the nut to a torque of 130 - 170 Nm and remove the tool.

Shimming

Place the finger of the dial gauge on the end of the shaft (7). From the front of the housing, pull hard on the shaft, turning alternately from left to right to correctly seat the cones in their bearing cups.

Set the dial gauge to zero. In relation to the clearance measured, select a definitive thickness for shim (11) in order to provide a pre-loading of : P1 = 0.10 to 0.20 mm maximum.

Preferably shim to the maximum tolerance. Place the locking tool on the shaft, loosen nut (3) and take off the pinion (1).Take off bush (8) complete with bearing cone (9) from shaft (7).

Remove bearing cup (10) from the housing. Place shims (11) selected during operation 56 between spacer (12) and bearing cup (10). Slide the bush (8) and cone (9) assembly onto shaft (7). Proceed with the reassembly phase.