The determine shows the vacuum clutch system. This type of clutch employs the prevailing vacuum from the motor manifold to operate the clutch. The vacuum clutch includes a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  This helps prevent the transmission shaft and clutch plate from tilting up https://stephenturpn.blue-blogs.com/40208037/a-simple-key-for-clutch-plate-unveiled