A rotary transmission coupling
A rotary transmission coupling (1) is disclosed for selectively providing drive to an output such as a driven wheel (115, 116) of a motor vehicle (100). The rotary transmission coupling (1) includes a friction clutch (2) and a hydraulic actuator assembly (20) that receives fluid at pressure from a remote pump (206, 216) controlled by an electronic control unit (202). The actuator assembly (20) includes a hydraulic actuator formed by a body (21) that slidingly supports a piston (25) used to operate the friction clutch (2). The body (21) is restrained from rotation by a number of spigots (24, 35, 36) that allow limited translation of the body (21) to accommodate tolerance build-up within a transmission assembly (123) of which the rotary coupling (1) forms a part. The hydraulic actuator is attached to a clutch cover (4) of the friction clutch (2) such that the reaction force from the hydraulic actuator is resisted solely by the clutch cover (4) and is not transferred to any other components of the rotary transmission coupling (1).