Abstract: A retainer for a crossover tube of a ball screw between a rack piston and a worm shaft of a motor vehicle power steering gear. The ball screw includes a helical passage between the rack piston and the worm shaft, a U-shaped crossover tube on the rack piston, and a plurality of bearing balls which roll in a ball circuit defined by the helical passage and the crossover tube. The crossover tube retainer is a molded plastic arch straddling a linear segment of the crossover tube having a web bridging the gap between the crossover tube and the rack piston bore. The thrust of the bearing balls urging dislodgment of the crossover tube from the rack piston is reacted against the rack piston bore through the web of the molded plastic arch across a bearing surface of the web having a contour complementary to the contour of the rack piston bore above the molded plastic arch.