Mechanical reverse shuttle


Type tractors may be fitted with a Heavy gearbox featuring a mechanical reverse shuttle.
The reverse shuttle transmits movement commanded at the Dynashift into the transfer shaft installed at the front of the main gearbox, by the action of the dual gear.



The reverse shuttle assembly is located in the rear cavity of the input housing behind the Dynashift. It includes:
- two helically cut pinions (19) and (28) installed on two needle bearings (4) and (5). These pinions are respectively in constant engagement with the dual gear at the box main input drive and reverse-drive idling gear (17)
- twin-cone synchromesh assembly (34), the hub is locked by the splines on secondary shaft (2)
- a synchromesh-control selector rail and fork assembly.
- secondary shaft (2) installed on two tapered roller bearings supported by two bearings in the input housing
- reverse drive idling gear (17) rotating on two tapered roller bearings installed on shaft (14) mounted in two bores in the housing.
The latter gear is in constant engagement with the front teeth of the gearbox dual input gear.

When the synchromesh slide is over on the right, it transmits movement to forward drive gear (19) in direct connection with the rear teeth of the gearbox dual input gear.

Reverse drive


Forward-drive gear (28) is in constant engagement with idling gear (17) which meshes with the front teeth of the gearbox dual input gear.


Parts List 
(1) Shim(s) (2) Secondary shaft (3) Bearing cone (4) Needle roller bearing (5) Needle roller bearing (6) Bush (7) Washer (8) Bearing cone (9) Bearing cup (10) Roller bearing (11) Screw (12) Bearing cone (13) Bearing cone (14) Idling gear shaft (15) Bearing cup (16) Spacer ring (17) Reverse-drive idling gear
(18) Bearing cup (19) Forward drive gear (20) Synchromesh slide (21) Rings (22) Rings (23) Cones (24) Synchromesh flanges (25) Locking device (26) Shoes (27) Synchromesh hub (28) Reverse-drive gear (29) Washer (30) Bearing cup (31) Screw (32) Retaining plate (33) Housing (34) Synchromesh assembly

Split the tractor between the engine and gearbox.
Drain the gearbox and the intermediate housing.

Visually identify the contour of the plugs.
Remove the hydraulic clutch.
Remove the selector cover.
Remove the input housing.
Disassemble the locking device, the selector rail and the reverse shuttle fork.
Place the housing on a work bench in the vertical position. Remove the sling.
Disassemble the Dynashift.

Disassembling and reassembling the reverse shuttle


Remove screws (11), extract shaft (14). Remove gear (17) and bearing cones (12) and (13).
Drive out cups (15) and (18). Remove spacer ring (16).

Pair the cones and cups if they are to be reused.

Remove screws (31). Remove retaining plate (32), shims (1) and cup (30).
Extract secondary shaft (2).


1

Remove the assembly comprising pinions (19) and (28), synchro (34) (Fig.1) and washer (7).
Remove cone (8) and cup (9).
Separate the following parts on the pinion or synchromesh assembly:
- gear (19), bush (6), needle roller bearings (5), cones (23), rings (21), rings (22), synchromesh flanges (24), gear (28) and needle roller bearings (4).
If necessary, withdraw cone (3) from the shaft, remove washer (29), and drive out roller bearing (10).

Clean and check the parts and replace any that are faulty.
Check that the pipes and ports in secondary shaft (2), shaft (14), housing (33), synchromesh (34) and bush (6) are not blocked.
Ensure that the plug (rivet) is crimped into the housing, on the end of the lube pipe to the reverse drive idling gear.
If necessary, overhaul synchromesh (34).
If it was removed, refit washer (29) on shaft (2) then fit cone (3) in abutment on the washer, using a press and a suitable fixture.
Lubricate the shaft, the cones and the bearing cups.
Assemble gear (19) and bush (6) by positioning the inner recess towards drive hub (27) of the assembly comprising (34), needle roller bearings (5), cones (23), rings (21), rings (22), synchromesh flanges (24), gear (28) and needle roller bearings (4).
Refit the assembly comprising pinions (19) and (28), synchro (34) and washer (7) (Fig.1).
Centre the washer. Insert secondary shaft (2) through the front bore in the housing, into the pinion / synchro assembly.
Install shaft (2), with shoulder E in contact with the synchromesh hub (Fig.2).


2

If shimming of the secondary shaft proves to be necessary, otherwise continue the assembly operation.

Install cup (30), shims (1) and retaining plate (32) (Fig.2).
Coat screw (31) with Loctite 241 or equivalent; install and torque to 25 - 32 Nm.
Manually check the axial play and rotation of pinions (19) and (28) and shaft (2).
If shimming of the reverse-drive idling gear proves to be necessary.
Install idling gear (17) fitted with spacer ring (16), bearing cones (12) (13) and shaft (14).
Apply a light quantity of Loctite 241 or equivalent to screw (11); install and torque to 40 - 56 Nm.
Check with fingers for normal backlash of gear (17) and rotation of the complete gear train.
Install roller bearing (10).

Preparing and shimming the secondary shaft
Position the housing in a vice.
Calculate shim thickness E (1) to obtain a temporary clearance of 0.10 to 0.20 mm maximum.
Position cup (30), shims (1) as calculated earlier, and retaining plate (32).
Install and provisionally tighten screw (31) without Loctite to 25 - 32 Nm.

Shimming 
Place the feeler of a dial gauge on the extremity of shaft (2).
Exert a hard pull on the shaft, rotating it alternately right and left in order to correctly seat the cones in the bearing cups.
Adjust the dial gauge pointer to zero.
Depending on the clearance value J obtained, select a new thickness of shims C (1) to obtain a preload: P1 = 0.10 to 0.20 mm According to the formula: C = E + J + P1
If possible, set at the top value of the tolerance.
Remove screw (31), remove retaining plate (32).
Install final shims (1) selected at operation 42, on cup (30). Reinstall the retaining plate. Install and torque screw (31).

Preparing and shimming the reverse drive idling gear
Position the housing in a vice.
Install minimum spacer ring (16) in the groove of gear (17) then fit cups (15) and (18) in abutment on
the segment.
Position gear (17) per Fig.3 and cones (12) and (13) on the housing. Slide shaft (14).
Install screw (11) (Fig.3) without Loctite, and torque to 40-56 Nm.
Adjust shims to obtain a clearance: J2 = 0.05 to 0.18 mm.

Shimming
Apply the feeler of a dial gauge to gear (17) (Fig.3).


3

Exert a hard push on the gear, alternately rotating to right and left in order to seat the cones correctly in the cups.
Adjust the dial gauge to zero.
Depending on the value read on the dial gauge, select the definitive spacer ring (16) to obtain J2.
If necessary, remove gear (17). Drive out cups (15) and (18). Remove spacer ring (16). Install the spacer ring selected at operation 54. Install the cups. Reinstall the gear. Repeat operation 30.
Coat screw (11) with Loctite 241 or equivalent, install and definitively torque to 40 - 56 Nm.
Check with fingers for normal backlash at gear (17) and rotation of the gear train.

Reassemble the Dynashift
Reassemble the reverse shuttle fork, the selector rail and the locking device.
Install the input housing.
Install the selector cover.
Install the hydraulic clutch (pressure loaded).
Reassemble the tractor between the engine and gearbox.
Service the oil in the sumps and check the level on the sight glass located on the left of the centre housing.
If necessary, bleed the hydraulically controlled clutch.
Proceed to road test of all Dynashift controls.
Check the leak tightness of the hydraulic connections and the mating face of the selector cover.