Dynashift


The Dynashift is fixed on the front of the input unit. It is an hydraulically controlled gear shifting device that provides four gearbox input ratios. This function is provided by two epicyclic gear trains associated with two hydraulic clutches.
The design of the Dynashift allows selecting the four ratios while moving, without needing to disengage the clutch, using a lever located under the steering wheel.
The Dynashift unit is controlled by two solenoid valves installed on the low-pressure hydraulic line (17 bar). Both solenoid valves are monitored by the tractor’s electronic system.
- the primary epicyclic train, the main part of the input unit, used to transfer movement from the engine to the gearbox
- the secondary epicyclic train, for controlling the speed of the primary sun gear.

Primary epicyclic train
The movement comes in via primary ring gear (31) which is splined onto transmission shaft (7). This turns at the same speed as the engine. The movement exits via planet pinion cage (28) which is splined onto secondary shaft (53). Primary sun gear (64) is driven by the secondary epicyclic train. The speed of this sun gear determines the reduction ratio of the box.

Secondary epicyclic train
This epicyclic train is controlled by hydraulic clutches and brakes.
Secondary ring gear (34) is:
- either locked to transmission shaft (7) by three clutch discs (3) and cup washer (4) located in the front part of the unit,
- or locked in relation to the unit by three brake discs (15) and piston (22).
When not actuated, piston (22) is drawn backwards by twelve springs (20) and cup washer (4) via thrust plate (16). When it is actuated under pressure from the 17-bar circuit, piston (22) moves forwards, blocking brake discs (15) and pushing plate (16), which compresses cup washer (4).
The speed of the secondary ring gear stabilizes as follows:
- speed equal to the engine speed when the front piston is not actuated,
- speed null when the front piston is actuated.
Secondary sun gear (61) is either:
- locked on the secondary shaft by means of four clutch discs (50) and two cup washers (52) located on the rear part of the unit, or
- immobilized in relation to the unit by means of three brake discs (41) and piston (37).
When not actuated, piston (37) is pushed forwards by the cup washers and six springs (65). Under the effect of the 17-bar pressure, piston (37) moves towards the rear and blocks brake discs (41). It compresses cup washers (52) through the action of thrust plate (45), which frees the clutch discs on the
secondary shaft. By immobilizing secondary ring gear (34) or secondary sun gear (61), the speed of secondary planet-pinion cage (39) is modified. The secondary planet-pinion cage drives primary sun gear (64), which establishes the reduction ratio of the box.





Parts list 
(1) Secondary ring gear carrier (2) Intermediate plates (3) Clutch discs (4) Cup washer (5) Splined hub (7) Transmission shaft (10) Friction washer (13) Front cover (14) Clutch housing (15) Front brake discs (16) Thrust plate (clutch - brake) (17) Clutch plate (18) Screw (20) Springs (21) Spacer housing (22) Piston (23) Rivet (24) O’ring (25) Screw (26) O’ring (27) Ball bearing
(28) Primary planet pinion cage (29) Rivet (30) Screw (31) Primary ring gear (32) O’ring (33) Screw (34) Secondary ring gear (35) O’ring (36) O’ring (37) Rear piston (38) Clutch plate (39) Secondary planet pinion cage (40) Reverse shuttle unit (41) Rear brake discs (42) Housing (43) Screw (44) Clutch plate (45) Thrust plate (clutch-brake) (46) Screw (47) Cover (48) Intermediate plates (49) Retaining ring (50) Rear clutch discs (51) Friction washer (52) Cup washers (53) Secondary shaft (54) Splined hub (55) Circlip (56) Spacer
(57) Ball bearing (58) Ball bearing (59) Rear clutch housing (60) Retaining ring (61) Secondary sun gear (62) Retaining ring (63) Needles (64) Primary sun gear (65) Springs (66) Screw (68) O’ring (69) Circlip (70) Stop (71) Shim(s) (72) Retaining ring (73) O’ring (74) Plug (75) Oil splasher (76) Stud washer (77) Spring washer (79) Washer (80) Circlip

Explanation of gearbox ratios




Ratio A : 1/1.620 reduction 
Pistons (22) and (37) simultaneously receive the pressure of the 17-bar circuit. Secondary ring gear (34) is locked to the housing by the action of the front brake. Secondary sun gear (61) is locked to the housing by the action of the rear brake. Consequently, the secondary epicyclic train is locked. Primary sun gear (64) is blocked. The reduction ratio is determined by the primary epicyclic train only. The kinematics are conventional, the movement entering via the ring gear and exiting via the planet pinion cage, with the sun gear remaining fixed.



Ratio B : 1/1.386 reduction 
Front piston (22) is under pressure. Secondary ring gear (34) is locked to the housing by the front brake.
Rear piston (37) is not under pressure. Secondary sun gear (61) rotates with secondary shaft (53) (clutch engaged). Secondary planet-pinion cage (39) turns at low speed, driving primary sun gear (64). The reduction effect is therefore lower.



Ratio C : 1/1.1704 reduction 
Rear piston (37) receives the pressure. Secondary sun gear (61) is locked to the housing by the effect of the rear brake. Front piston (22) is not under pressure. Secondary ring gear (34) rotates with transmission shaft (7) (clutch engaged), giving a speed higher than that of secondary planet-pinion cage (39). Primary sun gear (64) is driven by secondary planetpinion cage (39), at a speed greater than for ratio B. The reduction effect is therefore lower still.



Ratio D : Ratio 1/1 
Neither piston is actuated. Both clutches are therefore engaged. Secondary ring gear (34) rotates with transmission shaft (7). Secondary sun gear (61) is locked to secondary shaft (53), resulting in mechanical locking of the complete system. The ratio is consequently 1:1 (direct transmission).