Abstract: A hydrostatic coupling assembly for use in the driveline of a motor vehicle includes a first coupling part (3) and a second coupling part (4); a displacement machine (22) having a first rotor (23) which is eccentrically supported relative to one of the coupling parts (3, 4), and a second rotor (25) which is connected to the other one of the two coupling parts (3, 4). The first rotor (23) and second rotor (25) form displacement chambers (31) for hydraulic fluid thereby creating a pump. An annular chamber (50) communicates with the displacement chambers through first and second connecting channels (34, 35). A sliding sleeve (38) is axially displaceable between an open and closed position in which the outlets of the first and second connecting channels (34, 35) in the annular chamber (50) are open or closed, respectively.