Gearbox – Mainshaft


The mainshaft (7) fitted to Heavy gearboxes rotates on two taper roller bearings (9) (10) and (20) (21) lying in the two lower bearings of the main gearbox. The input gear (1) fitted at the front, engages with the shaft via splines. It is held by Belleville washers (2) fixed by the special cone-locking bolt (3). The Belleville washers also provide a constant load on bush (8), the synchromesh hub (16) and the shoulder of the shaft. This flexible assembly permits permanent contact of the stated parts, when forces are applied to the gears. Between the two lower bearings, the shaft bears the freely rotating driving pinions of 2nd gear (13) and 1st gear (19), as well as the synchromesh assembly of 1st and 2nd, the hub of which engages splines on the shaft. At the rear, it bears the freely rotating driving pinion of 4th gear (24) and the synchromesh assembly for 3rd and 4th gear. The rear bore receives bearing cup (22) of the taper roller bearing of the output shaft. The lubrication of 1st gear pinion and the bush of the 2nd gear pinion are ensured by a central channel and radial drillings.
The preloading of the bearings is adjusted by means of shims (11) placed behind bearing cup (10). The input pinion (1) is shimmed by means of shims (38) (39) fitted on the special bolt (3) to obtain a flexing of the Belleville washers (2).


Parts list
(1) Input pinion (2) Belleville washers (3) Special bolt (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 pinion
(14) 2nd gear synchromesh bearing cone (15) 2nd gear synchromesh ring (16) 1st - 2nd synchromesh (17) 1st gear synchromesh ring (18) 1st gear synchromesh bearing cone (19) 1st gear driving pinion
(20) Bearing cone (21) Bearing cup (22) Bearing cup (24) 4th gear driving pinion (25) 4th gear synchromesh bearing cone (26) 4th gear synchromesh ring (27) 3rd - 4th synchromesh (29) Snap ring (30) 3rd gear synchromesh ring (32) 3rd gear synchromesh bearing cone (38) Shim(s) (39) Spacer


To dismantle the mainshaft, it is necessary to remove the gearbox.
Uncouple the 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

Special point 


To remove the bearing cone (25), the synchromesh (27) and the 4th gear driving pinion (24), it is necessary to remove circlip (56) from the machined throat of the mainshaft. Then to push back pinion (57).
Take off the snap ring (29). Remove 3rd - 4th gear synchromesh (27) and mark its position.
Remove the synchromesh ring (26), the bearing cone (25) and the pinion (24).
Keep the synchromesh ring and bearing cone together if they are to be re-used.
Keep the shaft under rotation by using a locally manufactured tool and by using a 4 WD clutch, ref.
3617232M1.
If necessary, remove lubricating pipe (4) and spring (6).
Unscrew bolt (3) by means of a 32 mm socket and a suitable length extension.
Remove shims (38) (39), Belleville washers (2) and input pinion (1).
Remove bush (8) fitted with cone bearing (9).
Remove the tool. Take out the shaft from its housing with the 1st gear pinion (19) located at the rear, through the bearing aperture, while maintaining the fork, pinion and 1st - 2nd gear synchromesh assembly.
The extracting of the 1st - 2nd gear fork from the housing must be accompanied by the synchromesh assembly (16) and the 2nd gear driving pinion (13).
Remove the whole assembly (synchromesh, 2nd gear pinion assembly and fork) through the selector cover aperture.
Take off the bearing cups (10) (21).
In the case of re-use, keep cups and cones together.
Remove shims (11), spacer (12).

Where necessary, extract the bearing cones (9) (20), cup (22). Take off snap ring (5) from bolt (3).
Clean and inspect the components. Replace any defective parts.
Check that the central channel and radial ports of shaft (7) are not blocked.
If disassembled, with the aid of a press and a suitable fixture, respectively insert bearing cones (9)(20) on bush (8) and shaft (7). Position the snap ring (5) in bolt (3). Insert bearing cup (22) in shaft (7).
Lubricate the bearing cones and cups.
Install cup (21).
Place the spacer (12), the shims (11) selected during operation 59 and the bearing cup (10) in the bore of the housing.
- The shims (11) must be fitted between the spacer (12) and the bearing cup (10).
Check for wear on syncromesh rings (15) (17) against bearing cones (14) (18).
Assemble the 2nd gear pinion (13), bearing cone (14), synchromesh ring (15), 1st - 2nd gear synchromesh (16), 1st gear synchromesh ring (17) and bearing cone (18) on the workbench.
Install the entire assembly between the separations with the 1st - 2nd gear fork correctly positioned (Fig. 6).
Slide in the shaft and 1st gear pinion (19) through the rear of the housing while holding the pinion / synchromesh assembly.
Slide synchromesh ring (8) fitted with bearing cone (9) on to the shaft (7).


Install the pinion (1), the Belleville washers (2) positioned, and the shims (39) (38) determined during operation, along with bolt (3).
The shims (38) must be placed against the shoulder of the bolt (3).
Hold the shaft in place. Tighten bolt (3) lightly smeared with Loctite 270 to a torque of 320 - 360 Nm. Remove the tool. Manually check the rotation of the shaft.
If disassembled, fit spring (6) and lubricating pipe (4) with bolt (3).
Check for wear of synchromesh ring (26) against cone (25).
Install the pinion (24), cone (25), synchromesh ring (26) and the 3rd - 4th gear synchromesh (27) while respecting the direction of assembly.
Advance pinion (57) on the intermediate shaft and place circlip (56) in the throat without bending it and ensuring that it is correctly fitted.
Place snap ring (29).

Manually check:
- the axial clearance of the pinions
- the rotation of the shaft and its gear train.
Install the output shaft.
Install the input unit.
Install the selector rails. Adjust the forks and selectors of 1st - 2nd and Hare / Tortoise.
Replace the selector cover. Check that changing of the gears is correctly carried out and that the Hare / Tortoise position is present.
Connect the gearbox to the engine.
Reconnect the tractor between the gearbox and the intermediate housing.
Check the oil tightness of seals and hydraulic unions.
Road test the clutch controls, the reverse shuttle, the Hare / Tortoise range of gears and the A, B, C, D ratios of the Dynashift.

Shimming the input pinion 


Place the shaft (7) in a vice fitted with jaw protectors. Provisionally fit the synchromesh (18), the ring (8), input pinion (1), the Belleville washers (2) without the shims (38) (39). It is essential that special bolt (3) is tightened to a torque of 30 Nm maximum.
Place the dial gauge index on the end of the shaft, measure axial clearance of pinion (1).
In relation to the clearance measured and the thickness of the shim removed (39), select shim thickness (38) to obtain a flexing of the Belleville washers of between 1.25 mm and 1.75 mm.
If the axial clearance is greater than 1 mm, it is recommended to reduce it by adding only one shim (38) in order to measure it again with greater precision.
Take out bolts (3) and the elements provisionally fitted. Go on with the final assembly of the shaft and carry out its shimming.


In cases where input pinion (1) is replaced on the tractor, the shimming method is identical. First temporarily remove the cup (10) and shims (11) (12) in order to eliminate the preloading effect on bearings (9) (10) and (20) (21). When the shimming of the pinion is completed, replace the shims and the cup.

Shimming the shaft

Determine the thickness of the shim(s) (11) in order to obtain a temporary clearance of approximately 0.10 mm to 0.15 mm, while awaiting the shimming with preloading. It is essential to place the spacer (12) against the housing, previously determined shims (11) and cup (10).
Install the shaft locking tool. Tighten bolt (3). Remove the tool. Proceed with the shimming.

Place the index of the dial gauge on the end of shaft (7).
From the front of the housing, pull hard on the shaft while turning it left and right to seat it correctly in the bearing cups and cones.
Reset the dial gauge to zero.In relation to the clearance read on the gauge, select the correct thickness for the definitive shims (11) in order to obtain a preloading of: P1 = 0.10 mm to 0.20 mm maximum.


Install the locking tool on the shaft. Unscrew bolt (3). Take off the shims (38) (39), the Belleville washers (2) and the pinion (1).
Take out bush (8) fitted with bearing cone (9) and cup (10).
Place the shims (11), selected in operation 59, between spacer (12) and cup (10).
Install bush (8) fitted with cone (9), pinion (1), Belleville washers (2) and shims (38) (39) placed.
Tighten bolt (3) smeared with Loctite 270 to a final torque of 320 - 360 Nm. Remove the tool.
Manually check the rotation of the shaft and its gear train.