Abstract: Apparatus responsive to fluid pressures and capable of providing fluid under pressure to provide a unit which may selectively be used as a fluid motor or a fluid driven motor pump unit depending upon fluid directing and control structures and with minimal modifications to achieve the various desired functions. The unit consists of a pair of radially arranged units which units are known in the art as gerotors and which therefore includes a shaft for mounting or driving a first gear rotor of a first size, a rotor ring which is provided for both orbital and rotational movement with respect to the first gear rotor and with respect to a stationary ring gear surrounding the rotor ring. Valving plates including stationary and moving plates are provided to control fluid flow either between chambers formed by the various gear members and rotor ring for parallel flow when the unit is operating as a motor or individual chamber flow when the unit is operated as a motor pump.