Heavy gearbox - Output shaft


The output shaft fitted to Heavy gearboxes with mechanical reverse shuttle or Power shuttle, transmits the rotation supplied by the different gears to the drive pinion, via a coupling sleeve or a coupler (an option with the creeper gearbox). It is fitted on the lower transmission line at the rear of the gearbox.
The output shaft is supported by two taper roller bearings; the first is centred in the bore of the mainshaft and the second in the rear bearing.
The shaft supports:
- the 3rd Hare gear (35) fitted on two taper roller bearings and comprising bearing cups and cones (33) (34) and (36) (37).
- the synchromesh and the twin Hare / Tortoise cones assembly (69)
- the Tortoise gear (40) which is free mounted on the shaft (47).
A seal ring (28) fitted on washer (31) maintains lubricating pressure in the channel. The calibrated port in washer (31) allows for decompression in the cavity located behind the bearing cone (23). A channel drilled in the hub lubricates both cones of the syncromesh (69). The pre-loading of bearings (22) (23), (33) (34), (36) (37) and (43) (44) is carried out by means of shim(s) (45) placed behind the bearing cup (44).

Designation of double cone synchromesh components


Parts list
(22) Bearing cup (23) Bearing cone (28) Seal ring (31) Special washer (33) Bearing cone (34) Bearing cup (35) 3rd Hare gear (36) Bearing cup (37) Bearing cone (40) Tortoise gear (41) Locating pin
(43) Bearing cone (44) Bearing cup (45) Shim(s) (46) Rear bearing (47) Shaft (48) Bolt (69) Hare / Tortoise synchromesh (double cone)
(70) Synchromesh ring (creeper gearbox option)
F : Rear bearing (creeper gearbox option)
G : Syncromesh flange
P : Lubricating channel
R : Groove


Uncouple the tractor between the gearbox and the intermediate housing.
Remove the selector cover.

Removing and install the selector rails and forks

Remove the selector rails and forks from the gearbox.
Clean and inspect the components. Replace any defective parts.
Install the forks and the selector rails.

Removing, install and shimming the shaft

- If the tractor is fitted with the creeper gearbox option, remove the reduction unit.
Remove the rear bearing (46). By opening the plate located at the rear underside of the gearbox, maintain the gear train in place. Pull on the shaft and remove it.
Through the open selector cover, remove the entire synchromesh unit (69), the 3rd Hare gear (35) with the bearing cones (33) (37), special washer (31), bearing cone (23) and Tortoise gear (40)


Clean and check the components. Replace any defective part.
Check that the channels in shaft (47) and the decompression port of washer (31) are not blocked.
If necessary, insert:
- cup (22) in the layshaft
- cups (34) (36) in pinion (35)
- cone (43) on shaft (47)
Install seal ring (28) in the throat of special washer (31).
Smear the special washer and the bearing cone (23) with miscible grease. Place cone (23) and washer (31), the seal turned towards the front in the bore of the mainshaft (7).
Insert shaft (47) without its pinion in the previously mentioned washer and cone.
Mark a line of paint “T” on the feed through, the synchromesh (27) and shaft (47) corresponding to the flat on washer (31) and that on shaft (47).
Remove the shaft while holding in place washer (31) and cone (23) without turning shaft (7).

In the housing, introduce:
- the Tortoise pinion (40)
- pinion (35), with mark “R” turned to face the synchromesh (69) and with cones (33) (37moderately smeared with miscible grease.
Install syncromesh flange “G” on the Hare / Tortoise pinions.
Lightly smear the cones and synchromesh bushes with miscible grease.
Install the synchromesh, the drilled hole “P” or the paint mark turned towards the Tortoise pinion (40).


Position and centre the Tortoise pinion by holding it via the opening of the plate located below and at the rear of the gearbox or by using two bolts “V” as shown in figure 3.
If necessary, with the help of another operator, engage the shaft with cone (43) in the pinion assembly by aligning the paint marks previously made on the shaft, synchromesh and feed-through of the gearbox.


Determine the thickness of the shim(s) in order to obtain a provisional pre-loading clearance of 0.10 to 0.15 mm approximately (see further on). Place bearing cup (44) in the bearing using the previously determined shims (45) and placing the thickest shim on the bearing cup side. Position the bearing with the locating pin (41) (tractors without creeper gearbox) on the gearbox housing using of bolts (48). Tighten to a torque of 57 - 67 Nm.


 Shimming
Place the index of the dial gauge on the end of the shaft (47).
Push the short protruding length of the shaft using of a suitably adapted vice jaw fitted with protection, and turn the shaft left and right in order to seat the bearing cones in their cups.
Set the dial gauge to zero.
Repeat operation 25, but this time while pulling.
In relation to the clearance shown, select the thickness of shim(s) required to obtain a pre-loading of:
P2 = 0.01 to 0.05 mm.
Remove bolts (48) and bearing (46).
Take off bearing cup (44) and fit the definitive shims (45) selected during operation 28.
Install the cup. Place the bearing. Tighten bolts (48) lightly smeared with Loctite 270 to a torque of 57 - 67 Nm.

Manually check the rotation of the shaft and its gear train.
Install the selector rails and adjust the forks.
Adjust the Hare / Tortoise selector and refit the selector cover.
Re-couple the tractor between the gearbox and the intermediate housing.
Check for the oil tightness of all seals and hydraulic unions.
Road test all controls.