Power Shuttle GBA20 gearbox Speedshift - Removing and install


Removing, splitting and disassembling the planet carrier assembly


Remove the brake disc (21), thrust plate (20), Belleville washer (18) and planet carrier assembly (50).


Put the planet carrier assembly on a workbench with the unit (9) turned upwards. Remove the screws (3). Separate the unit (9) from the hydraulic cover plate (25) while holding sun gears (6) and (7).


The text and figures in this section concern the disassembly of a planet carrier for a forward speed of 40 kphRemove the input sun gear (7), visually identifying the direction of the lubricating grooves.



Drive out the pins (8) using a drift and a hammer. The pins are fitted tight in the thickest part of the planet carrier with the lubrication hole turned towards the hydraulic cover plate (25). Remove the planet gears (12).


Recover needle roller bearings (16), spacers (14) and washers (17). Remove the output sun gear (6).

Disassembling the hydraulic cover plate

Remove the splined hub (15).
Remove the intermediate plates (30), discs (42) and spring washers (43).
The clutch consists of:
- two friction discs;
- two spring washers;
- three intermediate plates.


Remove the piston (28) by lightly tapping the cover plate (25) on a wooden block or using a jet of compressed airRemove the seals (26) and (29) and discard them.

Reassembling the planet carrier

Clean and check all components. Replace those that are defective.
Lubricate the needle roller bearings (16).
Make sure that the radial holes and axial channel for the lubrication of pins (8) are not blocked. Tractor speed can be between 30 and 40 kph. Each speed is obtained by turning the planet gears and sun gears of the Speedshift epicyclic gear train. The sun gears have different numbers of teeth:
- sun gear (6): 36 teeth
- sun gear (7): 39 teeth
The text and figures in this section concern the reassembly of a planet carrier for a forward speed of 40 kph.
Put the output sun gear (6) in the unit (9), turning the sun gear lubricating grooves towards face "F" of the unit.


Install the needle roller bearings (16), separated by a spacer (14) in a planet gear (12). Put an "assembled" planet gear in the unit, the 18-tooth gear turnedEach double planet gear is identified with one, two or three punchmarks on one of its faces which is not necessarily the 18-tooth gear. In this case, make the same marks on the aforementioned gear using an appropriate pen. A punchmark corresponds to the alignment of two teeth.
Position the washers (17).


Centre the planet gear and washers with a guide pin Ø 16 mm, L = 80 mm.
Insert the pin (8) into the free bore on face "F" of the unit (9) Install it partially set backwith the radial lubricating hole "a" turned outwards and the end of central channel "C" turned towards face "F".


Repeat steps to assemble the two other planet gears. During these operations, position the three planet gears according to marks "R" so that they run in a line corresponding with "O".


After final assembly of the pins (8), check again that the marks are correctly aligned. Incorrect alignment may make it impossible to assemble combined parts or cause damage to the epicyclic gear train.
Install the input sun gear (7) with the lubricating groove turned towards the output sun gear (6).

Install the hydraulic cover plate

Clean and check all components. Replace those that are defective.
Make sure that the three holes of the 17-bar channel on the hydraulic cover plate (25) are not blocked.


Install the lubricated seals (26) and (29) and onto the piston (28).
Lubricate the mating faces of piston seals in the hydraulic cover plate.
Position the piston in the cover plate, turning the grooves towards the operator.
Install the piston (28) using a plastic hammer, gradually and alternately striking around the circumference of the piston. Check that there are no fragments of "O" rings after fitting. Install the splined hub (15).


Install an intermediate plate (30), a disc (42) and a spring washer (43). Continue stacking parts, ending with an intermediate plate. Arrange the cut section of spring washers in opposite directions.

Assembling the planet carrier

Screw two diametrically opposed guide studs in the hydraulic cover plate (25).
Assemble the planet carrier unit (9) on the hydraulic cover plate (25) while holding the sun gears (6) and (7). Position the unit and the cover plate so that the balancing marks (ground in marks) are on opposite sides as far as possibleReinstall the screws (3). They must be tightened to a torque of 14 - 20 Nm. Strike pins (8) definitively against the hydraulic cover plate (25) with a pin punch. Check that:
- the discs (42) are not compressed;
- the planet gears (12) and sun gears (6) and (7) turn freely.
Install the planet carrier assembly (50) on the shaft (5).
Position the Belleville washer (18)Position the thrust plate (20) in the housing (13). Install the brake disc (21) on the planet carrier assembly.

Assembling and install the front cover plate

Clean the cover plate. Make sure that the 17-bar channel and the lubrication channel are not blocked. Check that the sealing rivets (2) and (11) are present. Install the seals (22) and (23) on the piston (48).
Lubricate the mating faces of the piston seals in the cover plate (27).
Position the piston in the cover plate, turning the grooves towards the operator. Install the piston (48) using a plastic hammer, gradually and alternately striking around the circumference of the piston. Check that there are no fragments of "O" rings after fitting.
If work is necessary on the ring carrier (33):
- check that the channels are not blocked and that the ball bearing (40) is correctly crimped in its port. If necessary, Install the needle roller bearing (32) 18.13 to 18.33 mm from face "F";


- position the ring carrier on the cover plate, making sure that the low pressure (17 bar) and lubrication holes correspond respectively with those on the cover plate;
Install and tighten screws (34) and (41), lightly smeared with Loctite 242 or similar, to a torque of 25 - 35 Nm.
Check that the lubrication holes on the shaft (36) are not blocked.
Slide the shaft in the ring carrier. Reinstall the washer (38) and circlip (37).
Test-Install the new rings (31), making sure they turn freely in the grooves.
After this check, remove the rings and smear with miscible grease.
Install the rings in their respective grooves, making sure:
- that they do not exceed the circumference of the ring carrier;
- their ends overlap correctly. The slightest damage to rings may cause a leak followed by a pressure drop and incorrect operation of the Speedshift.

Smear the washer (39) with grease and Install it on the ring carrier (33).
Reinstall the new seals (1) on the housing (13).
Reinstall the shaft (36), ring carrier (33) and front cover plate (27) assembly using the same procedure as for removal.
Install and tighten the screws (24) to a torque of 36 - 46 Nm, with the thread lightly smeared with Loctite 242 or similar.
Remove the makeshift lifting tool.
Reinstall the Power Shuttle reverse clutch. Reinstall the input unit and the Power Shuttle forward clutch. Reinstall the spacer. Reconnect the tractor between the engine and the gearbox.