Ball screws are described that may be incorporated into other devices such as a pulley assembly or a differential device. The ball screws include a threaded shaft defining a central longitudinal axis with a threaded nut threadedly coupled thereto to define at least one track in between them. Each track forms a continuous loop around an infield protrusion and is filled with a plurality of rolling elements filling. Each rolling element has the same radius from the central longitudinal axis such that the nut can rotate at higher speeds without the rolling elements locking up as a result of centripetal force.