In heavy vehicles, the worm and nut with recirculating ball steering gear is a prevalent steering system.
This system features a worm gear, which is a threaded shaft known as the worm.
A ball nut, equipped with recirculating steel balls, is fitted onto the worm.
As the steering wheel rotates the worm, the balls traverse the threads of the worm and nut, thereby minimizing friction and causing the nut to advance along the worm.
This linear motion is subsequently transmitted to the sector shaft and pitman arm, which ultimately steer the wheels.
While the sector shaft supports this motion, the nut's direct interaction is with the worm.
Consequently, the accurate answer is worm.