Abstract: A hydraulic shock absorber unit provides automatic maintenance of a predetermined spacing between a sprung load and an unsprung portion where the mass of the sprung load is subject to change. The shock absorber unit includes a liquid filled cylinder in a cylinder body with a piston disposed in the cylinder for dividing the cylinder into a variable volume compression chamber and a variable volume rebound chamber. The piston is axially reciprocable within the cylinder and operates as a pump for a self-leveling fluid circuit. The shock absorber is connected between the sprung load and the unsprung load such that piston has a fixed spacing relative to a point on one of the loads, typically the sprung load. The cylinder has a fixed spacing relative to a point on the unsprung load. A lift chamber is axially disposed between the cylinder body and the sprung load for returning the shock absorber to a predetermined extension during transient loading conditions.