Power Shuttle


The power shuttle, also called “I.S.C.”, consists of two electro-hydraulically controlled clutches. It is so designed as to allow for reverse direction under load and can be fitted in parallel to the mechanical reverse shuttle to tractors equipped with Heavy Duty transmission.
- The power shuttle transmits the movement from the engine to the layshaft mounted on the front of the main gearbox by means of pinions located respectively to the rear of the input unit and at the gearbox input.
- A lever, mounted to the left under the steering wheel, controls both the power shuttle and A, B, C, D gear range of the Dynashift. It is also fitted with a position especially used for manual declutching of the transmission.
- Depending on the position selected by the operator (forward, neutral, reverse or manual declutching), the lever manages the progressive solenoid valves of the front and rear clutches by means of the electronic system of the tractor.
- The solenoid valves are located to the front and to the right of the gearbox on a clutch unit integrating the Dynashift hydraulic control system. A filter (60 microns) located under the right-hand selector cover,
upstream of the clutch units, provides additional filtering for oil supplying the solenoid valves (Dynashift clutches).
- A progressive sensor, screwed to the top of the box housing, sends shaft rotational speed information to the electronic system.
- Shifting of any forward gear to the corresponding reverse gear, or vice versa, is easy without declutching or stopping the tractor. This “assisted” gear reversal enables gradual changing of the operating direction, even at high travel speeds without abrupt changes in speed. The clutches slow down tractor movement until the required speed is reached so that the direction of operation can be reversed.
- The traditional hydraulically operated clutch pedal is replaced by an electro-hydraulic action maneuvering pedal. This pedal modulates the pressure in the front or rear clutches through the electronic system of the tractor and thus facilitates precise movements such as hitching tools.
The front and rear clutches of the Power Shuttle are of different design.




Parts list
(1) Pump unit (2) Pump cover (3) Shim(s) (4) Clutch cover plate (5) Locking ring (6) Splined ring (7) O’ring (8) Anti-extrusion ring (9) Snap ring (10) Seal (11) Circlip (12) Ball bearing (13) Screw (14) Lubricating pump (15) Sealing rings (16) Ring (17) Centering pin (18) Front clutch unit
(19) Input shaft (20) Pin (21) Circlip (22) Ball bearing (23) Snap ring (24) Seal (25) Belleville washers (26) Indexing ports (27) Drive hub (28) Front clutch piston (29) Front clutch discs (30) Front clutch intermediate plates (31) Lubricating pipe (32) Ball bearing (33) Front clutch cover (34) Planet carrier cover (35) Rivets (36) Seal (38) Rear clutch cover (39) Rear clutch piston (40) Rivets (41) Seal (42) Seal (43) Plate (44) Spools (45) Springs (46) Rear clutch intermediate plates (47) Rear clutch discs (48) Ring restrictor (49) Planet carrier (50) Pinion gear pin (51) Spacers (52) Double pinion gear (53) Input sun gear (54) Snap ring (55) Primary shaft (56) Snap ring (57) Ball bearing (58) Output sun gear (59) Single pinion gear (60) Needle bearings (61) Snap rings (62) Springs (63) Stop plates (64) Screw (65) Snap ring (66) Screw (67) O’ring (68) Ball bearing (69) Seal (70) Screw (71) Pin (72) Unions (73) 1.5 bar valve (74) Pipe (75) O’rings (76) Pipe (17 bar rear clutch) (77) 13 bar valve (78) Pipe (shuttle lubrication) (79) Screw (80) Flange (81) Seal (82) 500 micron strainer (83) Union (84) Plug (85) Seal (86) Lubricating pipe (87) Pipe (88) Union (90) Diagnostics connector (lubrication) (91) Union (93) Union (94) Pipe (95) O’rings (96) Union (97) Screw (98) Snap ring (99) Screw


The rear clutch consists of :
- an epicyclic gear train consisting of three double pinion gears (52) and three single pinion gears (59),
- a hydraulic braking device for planet carrier (49)
- a cover (38) supporting the front clutch and with an inner side machined to assemble hydraulic parts.
- The double and single pinion gears (52) (59) of the epicyclic gear train mesh respectively on the input and output sun gears (53) (58). The pins (50) are mounted idle and held in the planet carrier by plates (63). A central drilled channel and radial ports supply lubrication to needle bearings (60).
- The planet carrier braking device consists of an annular piston (39) and a plate (43) that is loaded by springs (62) and discs (47) integral with the planet carrier through splines.
- The intermediate plates (46) are immobilised by the pins (71).
- The fixed unit (1) performs two functions:
- it receives the low pressure supplying the front clutch via pipe (74),
- it acts as the body of the clutch lubricating and cooling pump.

The pipes (31) (86) connecting the pump unit (1) and cover (38) lubricate the rear clutch braking device. The pipe (87) provides the hydraulic link to the lubrication diagnostics connector.
The shims (3) located between clutch cover plate (4) and the fixed pump unit (1) provide the axial clearance for the front clutch.
Drive from the power shuttle is transmitted to a mechanical unit located in the rear compartment of the input box.



The front clutch consists of:
- a conventional type oil-bath multidisc clutch consisting of a cover (33), the rear side of which is splined to assemble the input sun gear (53),
- an input shaft (19) passing through the clutch cover plate (4) that separates the engine flywheel from the transmission oil. The shaft is constantly meshed with the damper secured to the engine flywheel. It is splined so as to rotate with the clutch unit (18) comprising the intermediate plates (30) and the discs (29) in which piston (28) moves,
- a drive hub (27) comprising the discs (29) and integral with the primary shaft (55). The front clutch is centered in the cover (38) of the rear clutch by ball bearing (32).


This unit comprises:
- a secondary shaft (1) and helical pinion (2) machined in one piece.
The shaft is mounted on two taper roller bearings having different cross-sections and is carried by two bearings.



The shims (3) fitted between bearing cup (16) and the rear casing (5) are used to preload the bearings.

Operating principle


Front clutch
When the lever under the steering wheel is in the Forward position, the solenoid valve is activated and supplies a pressure that moves piston (28). This, in turn, compresses the intermediate plates (30) and the discs (29) against cover (33). The movement from the engine to the gearbox complies with the following kinematics:
- input shaft (19) splined to unit (18)
- front clutch unit (18)
- intermediate plates (30)
- discs (29) compressed by the piston (28)
- hub (27)
- primary shaft (55)
- main box layshaft via the input pinion.
Simultaneously, the pressure applied behind piston (39) of the braking device drops and the planet carrier assembly (discs (47), intermediate plates (46) and epicyclic gear train) rotate freely.
Remark: When the control lever is pulled towards the steering wheel, a "manual declutching" position of the front clutch is produced.

Lubrication
During forward operation, the oil flow from the centre housing via the pump (14) is directed towards the intermediate plates (30) and the discs (29) via the ports of the front clutch unit (18) opened by movement of piston (28). At the same time, lubrication of the braking device of the planet carrier (discs (47) and intermediate plates (46)) of the rear clutch is interrupted.

Rear clutch
When the previously mentioned lever is moved from the Forward to Reverse position, the solenoid valve concerned is activated and supplies the piston (39) of the braking device of the planet carrier. The piston then presses on plate (43) which compresses discs (47) and the intermediate plates (46) against the front cover of the input unit and stops the rotation of the planet carrier. The movement from the engine is directly transmitted to cover (33) that is integral with the input sun gear (53) via splines, without passing through the discs and intermediate plates of the front clutch. Simultaneously, the pressure of oil in piston chamber (28) drops and frees discs (29) and intermediate plates (30).

The input sun gear then drives the double pinion gears (52) freely mounted on the pins (50) which, in turn, drive the single pinion gear (59), integral with primary shaft (55) thus reversing rotation of the output sun gear (58) splined to the primary shaft (55). The primary shaft then sends the movement from the engine to the layshaft of the main gearbox via the input pinion.
As with Forward operation, simply pull the control lever towards the steering wheel to obtain the “manual de-clutching” of the rear clutch. A valve screwed to the top of cover (38) ensures a small permanent bleed starting from 13 bar to provide an automatic bleed of the hydraulic supply of piston (39).

Lubrication
As piston (39) moves, it operates spools (44) that act as valves and compress springs (45) via plate (43). The spools have a drilled center channel and radial ports, allowing oil to flow to the channels in cover (38) and the channels in the front cover of the input unit, thus lubricating the discs (47) and the intermediate plates (46). Lubrication of the mechanical parts of the epicyclic gear train is via the lubricating system of the input unit.
At the same time, the lubricating oil flow to discs (29) and intermediate plates (30) of the front clutch is stopped, thus halting any possible driving of the discs through a drag effect.

Neutral position
In neutral position, the supply to the solenoid valves is cut, placing the front and rear clutches at rest and eliminating transmission of the engine movement to the gearbox. The oil flow is also interrupted. The pressure in the circuit opens the valve and directs the oil to the housing.
After replacement of a solenoid valve or solenoid, power shuttle hydraulic unit or one of the components of the transmission control unit, it is necessary to carry out clutch calibration again.