Heavy duty gearbox - Creeper unit


Tractor fitted with heavy duty gearbox may also be fitted, depending on the options, with a creeper gear reducer unit. This reducer unit (24) consists of a simple epicyclical gear train comprising a planetary carrier and a crown and placed at the rear of the heavy duty gearbox. The link fitted to the front right-hand side of the intermediate housing operates the control fork of the reducer via a cable linked to a lever located in the tractor cab.


The coupler can only be activated when the tractor is halted pinion (9). Moving the control lever towards the "Snail" position moves the coupler to the rear and connects it to the planetary carrier (20) via the intermediary of the coupler ring (22).


The rotational speed of the drive pinion is one quarter of that of the output shaft of the gearbox. In normal gears, when the coupler is moved forward the output shaft of the gearbox is linked to the drive pinion, thus ensuring direct transmission.

Lubrication
The lubricating of the epicyclical reducer is carried out by splashing caused by its moving components.

Parts list
(1) Nut (2) Ring (9) Drive pinion (11) Snap ring (12) Friction washers (13) Pins (14) Friction plates (15) Planetary gears (16) Crown ring (17) Spacers (18) Needle bearings (19) Intermediate housing (20) Planetary carrier (21) Snap ring (22) Coupler ring (23) Bolt (24) Planetary carrier assembly (reducer)
(26) Nut (27) Fork (28) Selector rail (29) Link (35) Locking stud (36) Spring (37) Plug (38) Pin (39) Index (40) O’ring (41) pin (42) Link (43) Bolt (44) Housing (45) Shim(s) (46) Splined bearing (47) Output shaft (48) Bolt


Removing and remounting the Unit

Uncouple the tractor between the gearbox and the intermediate housing.

Removing the unit
Take off ring (2) and bolt (23) fitted respectively to the output shaft (47) and the housing (44).
Remove the components making up the reducer assembly (24) on the gearbox.
- On heavy duty gearboxes fitted with a creeper gearbox, bearing (46) is different from that fitted to the standard version.
- Machined splines on its edge connect it to the crown ring (16).

Refitting
Carry out a visual inspection of all components.
Lightly smear the faces of the reducer with miscible grease and fit the friction washers (12) with their tabs located in the appropriate grooves.
Replace the reducer assembly on the output shaft.
- a machined area on the external diameter of the crown ring ensures that the rear cup of the layshaft of the gearbox stands clear.
- the cutaway part of the housing (44) faces downwards.
Check the correct positioning of the components and tighten bolts (23) smeared with Loctite 241 to a torque of 10 - 14 Nm. Manually check for the rotation of the gearbox output shaft.
Couple the tractor between the gearbox and the intermediate housing.

Disassembling, reassembling and adjusting the selector

Uncouple the tractor between the gearbox and the intermediate housing.
Disconnect the control cable fitted to the link (42).

Disassembly 


- To take off the coupler (29), it is necessary to remove drive pinion (1) from the hydraulic pumps. Remove plug (37), recover spring (36) and locking pin (35). Remove the selector rail assembly (28) and nut (26). If necessary, break the seal, unscrew and take off nut (26). Remove rear ring (2), take off the lug washer (3) and spring (12). Immobilize the pinion and remove bolts (4).
Extract pinion (1) from bearing (11) and simultaneously take out the assembly (pinion, fork and coupler) through the front of the housing.
Remove the control link (42) located on the right hand side of the intermediate housing. Drive out pin (38) and remove index (39). Recover the shim(s) (45) and remove pin (41) complete with o’ring (40).

Refitting  
Lubricate a new o’ring (40) and place it on pin (41).
Place the pin in the chamfered port located on the exterior of the intermediate housing (19).
- To limit the axial clearance, it is recommended to shim to a tolerance of 0.1 to 0.6 mm.

Shimming
- On the axle, place the approximate thickness of shims (45). Fit index (39) and partially place the pin (38). Refit the link (42) and bolt (43).
- Manually evaluate the clearance.
- The adjustment principle consists of obtaining the minimum clearance between the various components.

Action
- If the clearance is outside the maximum allowed tolerance, determine a new thickness of shims required. After shimming, check for correct orientation of the index and the link. Definitively insert pin (38), fit and tighten Allen screw (43).
Rearrange the assembly (pinion, coupler, and fork) in the intermediate housing. Immobilize the pinion again. Fit and tighten the bolts (4) lightly smeared with Loctite 241 to a torque of 72 - 96 Nm.
On bearing (11), replace in their correct positions the spring, lug washer and ring. Refit the selector rail and nut assembly. Adjust the fork (see operation further on). Couple the tractor between the gearbox and the intermediate housing. Reconnect the control cable and where necessary carry out its adjustment.

Adjustment 


- Fit locking stud (35), spring (36) and plug (37). Partially tighten the plug.
- Place coupler (29) in the F1 “creeper gear” position, the rear face thrusting against the M60 nut (1).
- In F2, maintain the fork thrust against the coupler.
- In F3, turn the selector rail (28) in nut (26) so as to place in contact the oblique side of groove G2 with locking pin (35) while simultaneously holding nut (26) against spotface B of the intermediate housing (19).
- Using a depth gauge, measure distance X1 between the front face of the selector rail and face A of the housing.
- In F2, maintain the fork thrust against the coupler.
- In F4, turn the selector rail in the nut so as to place the other oblique face of groove G2 in contact with the locking stud while maintaining nut (26) as previously.
- Measure distance X2 in the same way as X1.
- Determine the X adjustment position using the following formula: X = (X1 + X2) 2
- Provisionally position the selector rail (28) at dimension X.
- Place the coupler (29) in the "direct drive" position; manually check the locking of the control and the clearance between the fork and the coupler. Take care also that the coupler is not in contact with the hydraulic pumps drive pinion.
- If this check is satisfactory, take out plug (37), the spring and the locking pin.
- Degrease the threads of the selector rail and those in nut (26).
- Lightly smear the nut threads with Loctite, tighten the nut and definitively position the selector rail, in accordance with the previously calculated dimension X.
- Lock the nut by bending its collar into the machined slot on the selector rail.
- Replace the locking assembly. Tighten plug (37) to 50 - 70 Nm.

Disassembling and reassembling the epicyclical reducer

Disassembly 
Remove the unit. Take off the circlip (11). Remove the friction washers (12).
Drive out the pins (13) Remove the planetary gears (15) from the planetary carrier (20) taking care not to lose the needles (18), the spacers (17) and friction plates (14).
- The coupler ring (22) is inserted into the planetary carrier using a press. The snap ring (21) ensures additional locking of the various components.


Reassembly 
Inspect and clean all components. Replace any defective parts.
Fit each planetary gear with two rows of needles smeared with miscible grease and separated by a spacer. Replace the planetary gears and position the friction plates (14). Refit pins (13), correctly orienting them to correspond with snap ring (11). Place the snap ring. Manually check the axial clearance and rotation of each planetary gear. Lightly smear the faces of the reducer with miscible grease and fit the friction washers (12), with their lugs lodged in the appropriate grooves. Refit the unit.

Control adjustment

On lever "A" 


Place control lever “A” in the “Snail” position. Screw clevis (1) flush with the threaded part of the cable (6). Mount clevis (1) on lever "A" with clip (7). Tighten nut (2). Tighten nut (3) on the knurled sheath end (5). Fit the knurled sheath end and Grower washer onto the support piece. Tighten nut (4) while checking that the cable is not pinched.

On link "B" 


Place link "B" in the "creeper gearbox" position (coupler (29) engaging the splines of the planetary gear carrier (20) (Fig. 2) and with the fork locked).
Screw clevis (9) flush with the threaded adjuster of the cable (6).
Fit the clevis (9) on to link "B" using clip (10). Tighten nut (11).
Adjust the stop (12) using nut (13) on support (8) while checking that link "B" is still correctly locked. Tighten nut (14) and check that the cable is not pinched. Check the operation and locking of the control in the "direct drive" position.