Abstract: A base is secured to a mounting member extending from a towing vehicle and having an upstanding ball element. A retention member carried by the base is selectively movable to a position over a socket element which extends from a towed vehicle and which is detachably engaged downwardly over the ball element. The retention member limits the upward travel of the socket element and maintains engagement of the coupling. The retention member is held in position by lock means. A resilient member is disposed between the base and the retention member to prevent the retention member from rattling against the base.