Abstract: A pressure activated rotary clutch includes a sealed unit including a casing and a cover mounted to and rotatable about a rotating shaft. The unit includes a circumferentially extending outer wall and a circumferentially extending inner wall having an outwardly extending lobe having major and minor dimensions from said shaft and also a fluid passageway having an inlet on one side of said minor dimension and an outlet on the other side of said minor dimension. A flow control valve is disposed in the fluid passageway for controlling fluid flow through the passageway. A flow control valve actuator in communication with the flow control valve operates the flow control valve. A rotor fixed to the rotating shaft includes at least one vane for moving or pumping fluid through the fluid passageway when it is open and the shaft is rotated. The unit rotates independently of the shaft and rotor when the passageway is unrestricted.