A positive-displacement pump having an eccentrically positioned internal ring gear and pinion within a pump housing. Pressurized operating fluid is provided by the pump to actuate an actuation piston of a clutch unit, such as a double clutch unit. The clutch unit is drivingly coupled with the pump for movement between engaged and disengaged positions. At least one throughbore is provided in the pump housing within which throughbore the clutch actuation piston is guided.