Reverse clutch - power shuttle GBA20 gearbox


Disassembling and reassembling the reverse clutch


Remove the forward clutch. Remove the input unit. Remove the screws (70) and the cover plate (38). Recover the spools (44) and the springs (45)Remove the large springs (62) and the pins (71).


On the cover plate (38), remove:
- the plate (43),
- the seal (42) and discard it,
- the piston (39),
- the seals (36) (41) and discard them,
- the unions (72), the valve and the seal (75) from the 17 bar supply port.
Immobilise the planet carrier (49) using the immobilizing tool, ref. 3378240M1.
Remove the screws (99) from the cover plate (34) and remove the cover plate.
Remove the discs (47) and the intermediate plates (46).


Separate the output sun gear (58), held by the snap rings (61), from the primary shaft (55).
Remove the snap ring (56).
Remove the planet carrier (49) with the double and single planet gears (52) (59).
On the planet carrier (49), remove:
- the plates (63),
- the pins (50) and double planet gears (52) assembly Mark their position,
- the pins (50) and single planet gears (59) assembly Mark their position,
- the snap ring (98) and the bearing (57). The rotation of the planet gears around the pins (50) is on two rows of needle rollers (60), joined and separated by a spacer (51). When the planet gears and pins have
been removed, check that no needle roller or spacer remains in the planet carrier.
Clean and check all components. Replace those that are defective.
Check that the ports in the planet gear pins and the channels in the planet carrier are not blocked.
Where necessary, Install the planet gears with two rows of needle rollers smeared with miscible grease and separated by a spacer.
On the planet carrier, Install:
- bearing (57) and position the snap ring (98),
- double and single planet gears (52) (59) positioned,


- the pins (50), with the lubricating ports fitted facing those in the planet carrier (49). Each end of the pins (50) has:
- a port, one of which is closed off by a rivet (35) and the other is used to lubricate the planet gears;
- a flat section and a shoulder preventing any pin rotation or any side movement.
Install the partially assembled planet carrier. Position the snap ring (56) and the rear snap ring (61).
Position marks "R" (punch marks) on the double planet gears (52) so that they pass through a centre line meeting at "O". The mark on the front face of the planet gear corresponds to the alignment of two splines. It is mandatory to correctly position the punch marks before assembling the output sun gear (58).


Slide the output sun gear (58), correctly turned, on to the primary shaft (55), making sure that the punch marks for each planet gear remain in the required position.
Install the front snap ring (61).
Soak the discs (47) in a transmission oil bath for approximately 1 hour. Check that they are correctly impregnated.
Install the discs (47) and the intermediate plates (46) depending on the type of tractor.


Check that the centring pin (17) is present.
Install the cover plate (34). Check that it is correctly positioned on the planet gear pins (50) and in the centring pin.
Immobilise the planet carrier, using the same method as used during disassembly.
Install and tighten the screws (99)) to 36 - 46 Nm with its thread lightly smeared with Loctite 242 or equivalent.
On the cover plate (38), check for the presence of the rivets (40) at the end of the channels. 
Install:
- piston (39) with new lubricated seals (36) (41), gradually and alternately striking around the piston rim with a plastic hammer. Check that there are no seal fragments after fitting.
- plate (43) with a new lubricated seal (42), aligning the holes of the plate with those in the cover plate (38). Install the plate using the same method as used for the piston (39).The thickness of the plate (43) differs according to the number of discs and intermediate plates.
Install the pins (71) and the springs (62) in their respective locations on the input unit.



Smear the spools (44) and the springs (45) with miscible grease. Fit and fix the spools in each compartment of the cover plate (38), with the tips facing towards the unions. Slide and fix a spring (45) on each spool.
On the external face of the cover plate (38), fit three sufficiently long and equally spaced studs in the holes provided for the screws (64).
Install and position the cover plate, with the port of the valve facing upwards.

Before fitting the screws (70), it is mandatory to check that the spools (44) slide freely in each compartment of the front cover plate on the input unit. To do this, compress the springs (45), using a screwdriver passed through the tapped holes of the unions (72). If the springs cannot be compressed, investigate the cause. Pre-tighten the screws (70).
During pre-tightening, check that the spools (44) still slide freely. Also check that each end of the (large) springs (62) is correctly housed in its respective seat.
Tighten screws (70) to a final torque of 36 - 46 Nm. After completing the tightening, check again that each spool can move freely and returns to its initial position. A spool valve that is blocked open can restrict or interrupt lubrication of the forward clutch during operation.
It is mandatory to fit and tighten the valve fitted with its seal to 6 - 8 Nm max. Screw in the unions (72).
Install the input unit and the forward clutch.

Disassembling and reassembling the driving gear and shimming the shaft


Remove the forward clutch. Remove the input unit. Remove the reverse clutch. Remove the Speedshift unit.
Remove the screws (5) and the stop plate (8).
Recover the shims (3) and the cup (4).
Take out the secondary shaft (1), fitted with the bearing cone (6) and the unit (7).
Note and mark the assembly order of the driving gear (2). Remove this gear.
Recover the bearing cone (9). Extract the cup (10).
Check that the ports for the secondary shaft (1) and the housing channels (7) are not blocked.
Clean and check all components. Replace those that are defective.
Lubricate the bearing cups and cones before assembling.
Install the cup (10) in the housing. Install the bearing cone (9) in this cup.
Position the gear (2), correctly turned in the housing.
Install the bearing cone (6) against the shoulder of the shaft (1). Slide the shaft in through the gear (2) and the bearing (9).
Position the cup (4). Determine the thickness of shims (3) to obtain a temporary clearance of approx. 0.10 to 0.15 mm for final shimming with preload. Position the shims and the stop plate (8). Tighten the screws to a torque of 25-32 Nm. Position the unit (7) in a vice.

Shimming the shaft


Place the dial gauge feeler pin on the end of the shaft.
Pull on the shaft, turning it alternately from right to left to correctly "seat" the cones in the bearing cups.
Set the dial gauge needle to zero.
Depending on the clearance measured, select a new thickness of shims (3) to obtain a preload P1 so that: P1 = 0.05 to 0.15 mm. If possible, shim to the maximum tolerance.
Remove the screws (5). Remove stop plate (8).
Position the final shims (3) selected on the unit (7). Install the plate (8). Install and definitively tighten the screws (5) to a torque of 25 - 35 Nm, with their threads lightly greased with Loctite 242 or equivalent.
Manually check the rotation of the shaft (1).
Install the Speedshift unit. Install the reverse clutch. Install the input unit. Install the forward clutch.