A piston pump assembly with a rotatingly driven swashplate in driving relationship with a rocker arm and piston engaged with one end of the rocker arm. A spring urges the rocker arm and piston into contact with an annular ring carried by a bearing in the swashplate. The spring may be a separate leaf spring or may be formed integrally with the rocker arm. The rocker arm engagement with the piston uses a spherical ball-joint-like surface. The contact between each of the rocker arm and piston and the annular ring utilize spherical surfaces on the rocker arm and piston, with an elongated footprint on the rocker arm and a circular footprint on the piston. The piston is allowed a slight radial play in operation.