It is a traditional mechanism controlled by a fork: When there is no pressure on the fork: ENGAGED.

Control of clutch fork: Slave Cylinder (see Pl. 26).

The clutch fork is moved by a piston under the action of fluid under pressure from the hydraulic block:

- when there is an absence of pressure in the cylinder: no effort on the fork: engagement (fig.1)

- when the pressure becomes sufficient in the cylinder, the fork pushes the friction plate free of the action of the springs which bring it into contact with the flywheel: disengagement (fig.2)

The surface area of the piston is calculated so that a pressure (P) of the liquid in the slave cylinder gives:

- P: total de-clutching

- P1: transmission of a weak force close to 0mkg - called "slip".

As P decreases through P1 to P2, the transmitted torque increases up to the limit of the pressure plate.

Numerical values: P is limited to 65kg/cm2 approximately (see # servo-hydraulic, fig.3).

P1 is variable, according to the vehicle and condition, between 17 and 30 kg/cm2 approximately.

P2 pressure is determined by the load valve.

It is a traditional gearbox, with pinions always in mesh, the 1st and reverse gears have no synchromesh, the 2nd, 3rd, 4th gears do.

Control forks (see pl.26, fig.3)

This command is hydraulic: forced by fluid under pressure coming from the hydraulic block.

Each gear has its own cylinder of command, its deselection is ensured by a return spring.

Pressure of the fluid operating each piston:

- in the case of 1st and Reverse, must be sufficient to overcome the return spring

- in the case of 2nd, 3rd, 4th gears, must increase gradually according to time to ensure:

- operation of the synchromesh,

- the speed of synchronization (friction of the conical parts) given by the synchronization capacity,

- the movement of the pinion,

- keeping the gears engaged,

- pressure values (see Pl.24)