A closed hydraulic system (22) is provided for transmitting steering movement to a rear wheel steering assembly (16) in response to steering movement of a front wheel steering assembly (14). The front wheel steering assembly is controlled by a steering wheel (18) and a power steering assembly (20). The closed hydraulic system (22) includes a pump assembly (44) and an actuator assembly (46) connected together by conduits (48,50) to define closed fluid flow branches or fluid links (49,51) for moving a piston (94) in the actuator assembly in response to movement of a piston (72) in the pump assembly. Movement of the actuator piston is transmitted to the rear wheel steering assembly via a cam assembly (92) which effects same direction rear wheel steering for rather small front wheel steering angles and which effects opposite direction rear wheel steering for greater front wheel steering angles. System (22) may include a reservoir assembly (60) including a piston assembly (116) for maintaining a constant positive pressure in both branches, a dash pot (124) for preventing sudden steering angle changes of the rear wheels in the event of rapid fluid loss in either branch, and relief valve assemblies (126,126') for limiting the maximum pressure differential between the branches.