Gear Change Control Piston - Valves

The piston is moved:

- by the high pressure: positioning of the piston (fig.1)

The high pressure passes through channel (A-B) and acts under the section of the piston. A spring (r) is compressed in order to close the high pressure inlet in (A) when the pressure in the clutch cylinder, as in chamber (C), is between 60 and 65 kg/cm2 approximately: disengagement (fig.2). This piston then allows the passage of the high pressure towards the selector piston: no gear changing can be done before the gear change control piston is in position.

- at a point determined by the valves: displacement of the piston.

During the changing of a gear and after the interlocking, the force provided by the increasing pressure under the valve selected becomes higher than the force of spring (r) (in the position fig.2). The piston goes up, the pressure in the clutch cylinder and in chamber (c) (fig.3) becomes equal to the pressure remaining in the chamber (F).

Automatic clutch piston.

The piston is moved:

- by the high pressure: positioning of the piston (fig.1).

The high pressure passes through the channel (D,E) and comes to act on the section of the piston: a loaded spring (t) placed under the automatic clutch piston closes the high pressure inlet in (g) when the pressure in chamber (f) is slightly higher than P1* (fig.2).

- by the automatic clutch piston (called "piston de 38"): displacement of the piston (fig.3).

The operation of this piston allows the descent of the drawer.

Automatic Clutch Control - the piston, with a calibrated hole and resting against the spring (T), slides in the hydraulic block. The compression of the spring is a function of the pressure loss created by the flow of a volumetric pump (known as the Engine Feed Pump) passing by the calibrated hole.

* See # clutch cylinder.