Power Shuttle Gearbox - Selector rails


Tractors fitted with a gearbox with Power shuttle, the selector rails used for gear selection are located on the right-hand side of the gearbox and behind the control cover. The gear selector comprises the following selector rails for:
- 1st and 2nd gear
- Hare/Tortoise (Hi-Lo)
- 3rd and 4th gear
Each selector rail supports its own fork and respective selector and moves longitudinally in end-bearings.
The front bearing fixed on the rear part of the input unit is removable and serves as a support for the selector rails. The forks are adjustable, thus ensuring a functional clearance between the pads and the synchromesh sliding coupler.

Safety locking of the gearbox selector
The system comprises two cylindrical locks of different lengths.
- short locking pin: selector rail 1st - 2nd
- long locking pin: selector rail 3rd - 4th
Their extremities are spherical and one of them has an extended lug. Each selector rail is machined both to lodge and to allow movement of the locks.

Operating principle
Example: Ratio 1 engaged - Hare range
When the selector rail is moved to select 1st gear, it forces its lock to move out of its lodging place and to lock the range selector rail in the "Hare" position. At the same time, this lock pushes another lock that in turn locks the 3rd - 4th selector rail, thus prohibiting any undue movement that might block the gearbox.
The same reasoning applies to the Tortoise range and other gear ratios.


Parts list
(1) Selector rail 3rd - 4th (2) Short locking pin 1st - 2nd (3) Hare / Tortoise selector rail (4) Selector rail 1st - 2nd (5) Long locking pin 3rd - 4th (6) Gearbox housing (7) Selector 1st - 2nd (10) Locking pin (11) Spring
(12) Plug (13) Input unit housings (14) Reverse shuttle fork (15) Fork 1st - 2nd (16) Fork 3rd - 4th (17) Hare / Tortoise fork (18) Long spacer (19) Short spacer (20) Bolt (21) Pin (22) Removable front support (23) Rear support



Disassembling and reassembling selector rails and adjusting forks and gearbox selector

Uncouple the tractor between the gearbox and the intermediate housing.
Remove the selector cover.
On tractors fitted with a creeper gearbox, the reducer unit (1) located on the rear face of the gearbox does not hinder disassembly or reassembly of the selector.
Remove the bolts (20) from the selector (7) and forks (15) (16).
To carry out operations on the 1st - 2nd fork, use a short Allen key due to the limited space between the fork and the housing.
Disassemble the index assemblies (10) (11) (12) (18).
Push selector rail (4) towards the front and remove lock (2). Proceed in the same way for selector rail (1) and locking pin (5).
Take out selector rails (1) (4) through the rear of the gearbox.
Using a suitable pin punch, drive out pin (21) from the Hare / Tortoise fork (17).

Take out selector rail (3) through the rear of the housing.
Remove the 3rd - 4th (16) and the Hare / Tortoise forks.
The 1st - 2nd fork (15) cannot be removed from the housing unless the main shaft has previously been removed.
Clean and inspect the components. Replace any defective parts.
Install the selector rails, forks and selectors in the reverse order of disassembly.
During refitting, pin (21) on the Hare / Tortoise fork must be replaced.
Special points
- The short locking pin (2) locks selector rail 1st - 2nd.
- The long locking pin (5) locks selector rail 3rd - 4th.
- The index assembly (10) (11) (12) (18) places selector rail 1st -2nd.
- The index assembly (10) (11) (12) (19) places selector rail 3rd - 4th.
Adjust forks and selector (7) (see below).

Adjustment
The positioning of forks (15) (16) and selector (7) is obtained via the difference between the distance between the centre of threaded holes "Y" and mark "Z" on the selector rails (1) (4). A different forward or rearward movement of the forks is obtained by acting on bolt (20) as required. The adjustment of forks is carried out with the gear engaged.


Smear the plugs of the indexing assemblies (10) (11) (12) (18) with Loctite 542 or equivalent and tighten onto the housing. Lock fork (15) in 1st. Maintain the synchromesh sliding coupler against the pinion. Check that the rear pads are not in contact with the synchromesh sliding coupler by slightly moving the selector rail without moving the sliding coupler itself.
Repeat the operation (fork locked in 2nd), checking that the rear pads are not in contact with the synchromesh sliding coupler, by using the same method as in operation 13. If the pads are in contact with the sliding coupler, adjust the fork using bolt (20) lightly smeared with Loctite 221 or equivalent.
Proceed in the same way to adjust fork (16).

Tightening torques
- Bolt (20): 35 Nm without modifying its adjustment, Loctite 221.
- Plug (12): 50 - 70 Nm, Loctite 542.
Next, adjust selector (7) in line with the selector incorporated in fork (16).
Adjust the "S" Hare / Tortoise selector.
Install the selector cover. With the gear lever in neutral, check that locks (2) (5) are free in the rear bearing in the Hare / Tortoise range.
Couple the tractor between the gearbox and the intermediate housing.
Road test. Check:
- gear changing (all gears)
- correct operation of the Hare / Tortoise range.
Check oil tightness of the gearbox and intermediate housing mating faces, selector cover and hydraulic unions.