Abstract: When incorporating a rear wheel turning system having a mechanical system and hydraulic system, an end of the displacement transmission member, which transmits displacement of the output member of the rear wheel turning system to the hydraulic system and the rear wheel turning shaft, is fixed to the vehicle body in such a position that the leftward maximum displacement of the rear wheel turning shaft is equal to the rightward maximum displacement of the rear wheel turning shaft when the input shaft of the rear wheel turning system is rotated in one direction and the other by the same angles.

Abstract: A reference position detection method of a vehicle rear wheel steering apparatus in the present invention, is provided with steps of setting an input shaft and the yoke assembly at arbitrary angular positions rotating the input shaft by an arbitrary angle to pass a neutral angular position measuring a rotational angle .theta. of the input shaft and a moving amount .delta.1 of an output rod assembly upon rotation of the input shaft rotating the yoke assembly to pass a neutral angular position so that the output rod assembly is stroke-moved by a moving amount -.delta.1 from a stroke position defined by the moving amount .delta.1 of the output rod assembly rotating the input shaft by an angle -.theta. after rotating the yoke assembly, and measuring a moving amount .delta.2 of the output rod assembly; and determining, as a reference position of the yoke assembly, an angular position obtained by rotating the yoke assembly from the rotated state of the input shaft so that the output rod assembly is displaced by -.