Abstract: A steering shaft, linked with the dirigible wheels of an automotive vehicle and coupled with a hydraulic servomotor for rotation in either direction under the control of a main valve, has two abutments for alternately opening two normally closed ancillary valves in respective limiting positions of the shaft, these ancillary valves being inserted in branches of two feeder lines extending from the main valve to respective cylinder chambers of the servomotor. Either ancillary valve, when opened, connects one cylinder compartment of a differential valve to the feeder line then under low pressure, the other compartment of that differential valve being connected to a supply conduit whereby a pressure difference is created across a spring-loaded piston in that valve whose two compartments are interconnected by a bleeder line. The piston, upon being displaced by this pressure against its spring force, vents the supply conduit to the low-pressure side of the fluid source to arrest the servomotor.