Abstract: A control system of the hydraulic torque converter of a transport vehicle wherein the space formed by the converter wheels and the space of the coupling which locks said wheels are in communication, through a changeover valve actuated by a signal of the RPM transmitter of the engine shaft of the transport vehicle, with the discharge line of the pump, said line communicating with the source of fluid via a reducing valve. The system incorporates an auxiliary pump whose discharge line communicates with the discharge line of said pump through a check valve and, through a valve actuated by the pressure of fluid contained in the space of the locking coupling, with the source of fluid.

Abstract: A vehicle drive transmission comprising an air released main clutch connected between a torque convertor and multiple ratio gear transmisson. A lock up clutch for the convertor turbine and impeller is engaged by hydraulic pressure when an engine drive governor reaches a predetermined speed and opens a governor valve. The main clutch is released by a motor controlled by a solenoid valve which selectively connects the motor to a source of air pressure or to atmosphere via a restricted orifice and a normally closed air inlet valve. The restriction retards the engagement of the main clutch when the engine is rotating below the predetermined speed, and above said predetermined speed, the governor valve opens to engage the lock-up clutch and to open the air inlet valve whereby the main clutch may be engaged at a faster rate.