GBA20 gearbox - Creeper unit


The creeper speed reducer consists of an epicyclic gear train with a planet carrier and ring gear assembly fitted at the rear of the main gearbox. It is controlled by a lever located on the cab console and linked by a cable to a rod fitted on the front right-hand side of the centre housing. This rod moves the coupler control fork. Creeper gears can only be selected if the main gearbox is in the Tortoise range. The coupler (8) is splined to the connecting shaft (21). Moving the lever "A" to Snail position moves the coupler (8) back and engages it with the planet carrier (1) via its external teeth. The speed of the shaft (21) is 1/4 in relation to the output shaft. For normal gears, the gearbox output shaft is attached to the connecting shaft (21) when the coupler (8) is moved forward, thus ensuring direct drive. When the creeper range is selected, the Snail indicator light on the instrument panel comes on. 


When the Hare range indicator light flashes, this indicates to the operator that Hare position is engaged and shifting to Tortoise position is required. The electrical signal corresponding to selection of the creeper range is transmitted via switch "C", which is fitted on the control unit.


Parts list 
(1) Planet carrier (2) Friction washer (3) Cover plate (4) Lock washer (5) Screw (6) Snap ring (7) Coupler ring (8) Sleeve (9) Planet gears (10) Needle rollers (11) Spacer (12) Pin (13) Gear plate (14) Gear plate (15) Stop plate (16) Circlip (17) Planet carrier assembly (18) Friction washer (19) Ring gear (20) Centring pin (21) Link shaft



Removing the unit and the ring gear

Take off the right-hand hydraulic cover plate and, if required, the left-hand hydraulic cover plate.
Disassemble the PTO assembly.
2-speed PTO
Remove:
- the PTO top cover plate located at the rear of the centre housing;
- the driving gear;
- the intermediate shaft;
- the PTO clutch.
4-speed economy PTO
Remove:
- the PTO top cover plate located at the rear of the centre housing;
- the driving gear;
- the intermediate shaft;
- the PTO clutch.
Disassemble the sleeve / connecting shaft / coupler / assembly and the fork.

Removing the unit and the reducer ring gear
Remove the screws (5) and the washers (4)
Remove the cover plate (3).
Take out the planet carrier assembly (17) and the friction washers (2) (18).
Remove the ring gear (19). The centring pins (20) remain in the ring gear.
Remove the stop plate (15) without pulling on the output shaft.

Disassembling the planet carrier

Remove the circlip (16).
Drive out the pins (12).
Remove the gear plates (13) (14).
Remove the planet gears (9). Replace the planet carrier (1) if the coupler ring (7) is damaged.

Reassembling the planet carrier, refitting the ring gear and the unit

Check and clean all components. Replace those that are defective.
Install the planet gears (9). Use miscible grease in oil to fit the needle rollers (10).
Install the gear plates (13) (14).
Install the pins (12), directing them as required to fit the circlip (16).
Install the circlip (16). Manually check the axial clearance and rotation of each planet gear.
Position the stop plate (15) and the ring gear (19) on the housing.


Install the friction washers (2) and (18) smeared with miscible grease on the planet carrier (1).
Slide the planet carrier onto the output shaft.
Position the cover plate (3). Tighten screws (5) to a torque of 34 - 52 Nm.

Reassemble the fork and the rear sleeve / connecting shaft / coupler assembly.
Reassemble the PTO assembly.
2-speed PTO
- Install the power take-off clutch.
- Install the intermediate shaft, the driving gear and the PTO top cover plate.
4-speed PTO
- Install the power take-off clutch.
- Install the intermediate shaft, the driving gear and the PTO top cover plate.
Install the left-hand hydraulic cover plate (if removed) and the right-hand hydraulic cover plate.
Carry out a road test of the creeper unit.
Check PTO and PTO brake operation.

Adjusting the control

Place control lever A in the Snail position. The control lever may be located in two positions on the right-hand console, depending on whether or not an auto-hitch is fitted.


Screw the clevis (1) level with the end of the threaded part of the cable (6).
Install the clevis (1) onto lever A with the clip (7). Tighten the nut (2)Screw the nut (3) on the sheath end (5).
Install the sheath end and the Grower washer on the support. Tighten the nut (4). Check that the cable is not pinched.
Place connecting rod B in the "creeper" position (reducer dog (8) engaged towards the rear), fork locked.
Screw the clevis (9) level with the end of the threaded part of the cable (6).
Install the clevis (9) to rod B using the clip (10). Tighten the nut (11).


Adjust the stop (12) with the nut (13), making sure that connecting rod B is still firmly locked.
Tighten the nut (14). After tightening, check that the cable is not pinched.
Check that the control is locked in the "direct drive" position.