Abstract: A self-leveling combined shock absorber and liquid spring assist unit comprising a pair of tubular structures of the piston and cylinder shock absorber type, one of which defines a load bearing spring chamber and the other of which includes an elongated displacement member for the spring chamber, the displacement member being tubular and cooperating with a pump rod to provide a pump-up function for the unit. An improved pump check valve arrangement between the end surface of the displacement member and the exterior annular surface of the pump rod is provided for controlling the flow of hydraulic fluid between the pump chamber and the load bearing spring chamber which comprises an annular body of elastomeric material having an annular anti-extrusion washer of rigid material embedded therein which is spring urged into sealing engagement by a coil spring and held in assembled relation by a rigid tubular element fixed to the exterior periphery of the displacement member.