Recirculating ball

Recirculating Ball , also known as recirculating ball and nut or worm and sector, is a steering mechanism, commonly found in older vehicles. Mercedes-Benz was among the last large automobile manufacturers to use this technology. Today, most steering systems use the rack and pinion system.

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.