A ball screw assembly has an axially extending screw with an external helical groove and a nut with a through bore for receipt of the screw. The through bore has an internal helical groove adapted for cooperation with the external helical groove to define a ball raceway. A plurality of load bearing balls is disposed in the raceway for rolling contact with the internal and external grooves. A spacer is disposed between adjacent ones of the load bearing balls to prevent the balls from contacting one another. Each of the spacers has at least three pairs of diametrically opposite concave dimples adapted for contact with the load bearing balls at separate times from one another.