Recirculating ball, also known as recirculating ball and nut or worm and sector, is a steering mechanism commonly found in older vehicles, and most commonly rack and pinion steering is used instead. However, some significant manufacturers including DaimlerChrysler and General Motors still use this technology in some models, for example in the Jeep Wrangler.
A worm gear on the end of the steering shaft has a spiral groove filled with ball bearings, all encased in an assembly called the ball nut or steering gear nut. The nut has grooves on the inside to accept the bearings. As the steering wheel is turned, the nut moves up and down along the worm gear. A sector gear transmits the motion of the nut to the steering linkage, causing the vehicle's wheels to turn.