Steer gearings

The recirculating ball construction results in a friction free contact between the
nut and the worm. When the steering wheel turns to the left, the ball bearings
roll between the worm and the nut and work their way upward in the worm groove.
When the ball bearings reach the top of the nut, they enter two ball guides and
are directed downward into the worm groove at a lower point. When the steering
wheel is turned to the right, the ball bearings circulate in the opposite direction.