Mechanical reverse shuttle GBA20 gearbox - Removing and install the Selector cover plate


Removing and install the cover Plate

Immobilise the tractor. Chock the left rear wheel. Apply the hand brake. Chock between the frame and the front axle. Drain the gearbox. Raise the rear right-hand side of the tractor with a suitable jack.
Remove the wheel. Place an axle stand in position.
Remove the right-hand step and any surrounding parts that might hinder removal of the cover plate.

Removing the gear control (Fig.1)

1

- Disconnect the harness of sensor "C".
- Remove the ball joint (4).
- Remove the screw (3).
- Remove the pins (11).
- Disconnect the ball joint (5).
- Mark the adjustment of the cable (6). Slightly loosen the top nut (12). Separate the cable from the support (2).

Removing the reverse shuttle control (Fig.2)

2

- Disconnect the clips (1). Mark the adjustment of the cables (2).
- Loosen the lower nuts (3). Separate the cables from the support (4).
Disconnect the control cable (1) from the creeper or super creeper unit on tractors fitted with this option (Fig.4).
Remove the screws (3) (4) and the nut (6), marking the location of the earthing lug (2) and centring screws (4) (Fig.3).
If fitted, remove the support (2) of the creeper or super creeper unit control cable (Fig.4).
Release and remove the selector cover plate.


3

Clean the mating face of the gearbox and the cover plate.
Install:
- the 3rd - 4th fork in ratio 3 (Fig.4)
- the Hare / Tortoise range fork in Hare position. Before refitting the cover plate, check that the screw (1) is present (Fig.4).

4

Lightly smear the mating face of the gearbox housing with a sealing product such as Loctite 510 or equivalent.
Turn the finger (13) (Fig.5) to the left. Install the indexing rod A in Hare position.
Move the selector (2) and finger (36) to neutral position (Fig.4 and 5).
Install the cover plate on the gearbox, ensuring that:
- the finger (13) is positioned correctly in the forks (Fig.4 and 5);
- the finger (36) is engaged in the selector (2) (Fig.4 and 5).
Install the creeper or super creeper control cable support (if fitted).
Install the earthing lug (2). Install and tighten the screws (3) (4) and the nut (6) to a torque of 50 - 70 Nm. The centring screws (4) must be fitted as shown in Fig.3.
Depending on the option, reconnect and adjust the creeper or super creeper control. Reconnect the harness on the neutral position switch.
Reconnect:
- the gear control and sensor "C". 
- the reverse shuttle control. 
Using a grease gun, lubricate the joints of the gear control on the selector cover plate.

Legend (Fig.4 and 5)

5

A Indexing rod for locking the Hare/Tortoise fork
L Synchronisation of the Hare/Tortoise mechanism in Hare range
(3) Engaged gear (e.g. 3rd gear) (1) Screw (9) Selector cover plate (13) Finger (18) Locking stop

Check the shifting of all gears and the reverse shuttle. If required, adjust the controls. Check the operation of the mechanical reverse shuttle.
As required, Install any components removed previously from around the cover plate.
Install the wheel. Tighten the nuts to a torque of 400 - 450 Nm.
Top up the oil level in the housings. Check it using the gauge at the rear of the centre housing.
Remove the chocks between the frame and the front axle. Release the hand brake.
Check that the buzzer of the safety sensor vibrates correctly (ignition on, hand brake on and gear engaged).
Start the engine. When on the road, check:
- shifting up and down of the gear ratios;
- operation of the Hare / Tortoise range with the pulse button located on the lever;
- operation of the reverse shuttle in the forward and reverse positions.
33. Check the tightness of the selector cover plate mating face and of the hydraulic unions.

Disassembling and reassembling the gear selector and reverse shuttle mechanisms

Take off the cover plate. Secure it in a vice fitted with protective jaws.

Gear selector mechanism (Fig.6 and 7)

6

Remove the screws (1). Remove the key (4) and selector (3). Remove the support (2) from the cover plate.
Remove the screws (15). Separate the cover plate (9) and support (16) comprising the gear control assembly. If necessary, extract the locating rings (17).

7

On the cover plate (9)
Take off the Neutral position switch (28). Recover the seal (27) and ball bearing (18).
Extract and discard the seal (25).

On the support (16)
Take off the circlip (22), washer (21) and remove the spring (20).
Release the washer (33) and toggle switch (34), marking its position and profile. Recover the plunger (31). Extract the indexing rod (35).
If necessary:
- remove the screws (19);
- remove the speed grid (14);
- extract the locating rings (17).

Reverse shuttle selector mechanism (Fig.8 and 9)

8

Take out the set screw (4). Remove the rod (5).
Remove the screws (1). Separate the support (2) from the cover plate (9) (Fig.8).
Take out the set screw (38). Remove the finger (36) and pin (37) from the cover plate.

9

On the cover plate (9)
Remove any plugs screwed to the cover plate.
Extract and discard the seal (25).

Gear selector mechanism
If it was necessary to replace the guide ring (26), lightly smear its rim with Loctite 648 or equivalent. Install it up against the shoulder of the cover plate.

On the support (16)
If necessary:
- fit the locating rings (17),
- refit the speed grid (14) on the support (16),
- tighten the screws (19), lightly smeared with Loctite 270 or equivalent, to a torque of 29 - 37 Nm.
Check that:
- the plunger (31) and indexing rod (35) move freely in the support (16),
- the flat section of the toggle switch (34) slides normally on the finger (13).
Slide the pin of the finger (13) into the support (16).
Turn the toggle switch (34) as required. Install it onto the finger (13). Fit the washer (33).
Install the spring (20) and washer (21). Install the circlip (22).
Slide the plunger (31) into its cavity in the support (16).
Place the finger (13) in the Neutral position. Turn the indexing rod (35) as required and Install it.

On the cover plate (9)
Check that the locating rings (17) are present.
Install the gear control and support (16) assembly on the cover plate (9).
Lightly smear the thread of the screws (15) with Loctite 242 or equivalent. Tighten to a torque of 29-37 Nm.
Protect the lip of the seal (25) by surrounding the cylindrical end of the finger (13) with a flexible protection. Lightly smear the external rim of the seal with Loctite 542 or equivalent and slide it onto the protection. Remove the safety shield. Install the seal onto the cover plate using a suitable fixture.
Check that finger (13) is in the Neutral position.
Slide the ball bearing (18) into the depression on the toggle switch (34).

Checking the Neutral position switch (28)
Press manually on the button located at the end of the switch. Release the pressure and check that the button returns freely to its initial position. Repeat the operation several times. The check can be carried out using a multimeter.

10

Install the switch complete with its seal and tighten to a torque of 15 - 25 Nm.
Install the support (2), allowing a distance of 29 mm between the support and the 22 mm diameter of pin A (Fig.10). Lightly smear the screws (1) with Loctite 270 and tighten them to a torque of 25 - 35 Nm. This dimension must be met for the sensor to operate correctly.
Install the selector (3). Install and tighten the key.

Checking the locking system of the indexing rod (35)
In the grid (14), move the finger (13) from 1st to 4th ratio using the selector (3) (Fig.6) and manually check for the correct locking of the indexing rod in each of its positions. This indexing rod is linked to the Hare/Tortoise fork by an adjustable stop. If the replacement of certain components of the locking system was necessary, it is mandatory to readjust this stop.

Reverse shuttle selector mechanism
Assemble the finger (36) and pin (37). Lightly smear the thread of the set screw (38) with Loctite 242 or equivalent. Tighten this screw to a torque of 28 - 43 Nm.
If the guide rings (26) and (39) of the pin (37) needed replacing, lightly smear the rim of each ring with Loctite 648 or equivalent. Fit these rings up against their respective shoulders on the cover plate.
Install the support (2) on the cover plate (9). Lightly smear the thread of the screws (1) with Loctite 270 or equivalent (Fig.8). Tighten these screws to a torque of 25 - 35 Nm.
Slide the pin (37)/finger (36) assembly into the relevant bore on the cover plate.
Protect the lip of the seal (25) by surrounding the cylindrical end of the pin (37) with a flexible protection. Lightly smear the external rim of the seal with Loctite 542 or equivalent. Slide the seal onto the protection. Remove the safety shield. Insert the seal into the cover plate using a suitable fixture.
Install the rod (5). Lightly smear the thread of the set screw (4) with Loctite 242 or equivalent (Fig.8). Tighten this screw to a torque of 30-35 Nm.
Remove the cover plate from the vice. Refit it on the gearbox.

Assembling and adjusting the gear linkage and reverse shuttle control cables

Gear linkage - cab side

11

On the end of the rod (1) shaped with an angle of 166°, position the ball joint (2).
Tighten the nut (3).
Tighten the ball joint (4) up against the cable (6). Tighten the nut (5).
Place the support (7) on a workbench.
On the support, fit and tighten:
- the transmission lever
- the previously prepared rod and cable.
Install and secure the support onto the right-hand wheel housing of the cab. During this operation, ensure the rod and cable are inserted through the holes in the compartments. Install the shield rings.

Gear linkage - selector cover plate side

12

Screw the threaded rod (9) (fitted with nuts (3) and the ball joint (4)) onto the rod (1).
Tighten the ball joint (5) up against the cable (6). Tighten the nut (7).
Tighten and lock the other end of the ball joint (5) onto the cam (8).
On the previously fitted support (2) and lever "L", position the cam (8) and its extension block (10). Install the pins (11), and lock them in place with new pins. Install the ball joint (4) on the lever L. Install the washer and tighten the locknut.
Adjusting the rod (1) (Fig.12)
Turn the threaded rod (9) and ball joint (4) to obtain a dimension X of 17 ± 1 mm between the two nuts (3) when they are tightened.
Adjusting the cable (6) (Fig.12)
Adjust the sheath end to balance (as far as possible) dimensions "C" and "D". Tighten the nuts (12) without altering the adjustment.

Checking the proper engagement of each gear ratio and the position of the lever in the opening of the console.

This check should be performed with the gaiter of the transmission lever temporarily removed.
Engage each gear ratio. During this operation, check that the lever is never closer than 5 mm from the edge of the console.

Results
• Lever movement is not hindered in any way by the console
Adjustment is correct. Position the gaiter.
• Lever movement is hindered by the console

The lever is positioned incorrectly. Readjust the rod (1) (Fig.12) on the selector cover plate side in accordance with the following instructions:
- If the problem concerns the 1st or 3rd gear, reduce dimension X (Fig.12).
- If the problem concerns the 2nd or 4th gear, increase dimension X (Fig.12).
- If the problem concerns lateral movement of the lever between the 1-2 and 3-4 gear paths (Neutral position), adjust the cable sheath end (6) (dimensions C and D) (Fig.12). Tighten the nuts (12).

Reverse shuttle control cables - cab side

The assembled unit (4) and cables (2) (Fig.13) are entered in the catalogue as a complete assembly under a single reference. However, this assembly comprises a number of parts, most of which are available as spare parts.

Screw the clevises (1) level with the threaded end of the cables (2).
Install the clevises on the swinging lever (3). Install the clips. Tighten the nuts.
Slide the cable sheath ends into the slots provided on the unit (4). Position and tighten the cover plate (5).

Assemble the support (6) on the unit (4).
Attach the unit (4) / support (6) assembly to the base of the instrument panel (8). Ensure the cables are inserted into the hole in the cab floor. Position the feed-through conduits (7).
Position the floor mat.
Install the instrument panel cover and related components.
Position the reverse shuttle lever. Tighten the screw after smearing it with Loctite 242 or equivalent. Install the gaiter.

Reverse shuttle control cables – selector cover plate side

Screw the clevises (1) level with the threaded end of the cables (2).
Slide the sheath ends (3) into the slots provided on the support (4). The cable fitted with an adhesive colour strip must be fitted in the left-hand slot in the support (4). The adhesive strip can be stuck anywhere on the cable and is represented by the letter R in Fig.14. If the adhesive strip is missing, position the cables in the slots so that the shuttle lever position corresponds with the direction of movement of the tractor:
- forward: lever pointing upwards
- reverse: lever pointing downwards

Place the rod (5) in neutral (Fig.14).
Install the clevises (1) to the rod. Tighten the clevis nuts.

Cable adjustment (Fig.15)
Gradually and alternately adjust the tension of the cables (2) using the sheath ends (3) to achieve identical X and Y values, if possible. Tighten the nuts without altering the adjustment.



Check
Alternately engage the forward and reverse positions.
For each ratio, check that the rod (5) locks correctly without excessive cable tension.
Carry out a road test of the gear controls and reverse shuttle.