Nippon Seiko Recirculating Ball Gear Manual Steering

Fig. 1 Cross Sectional View Of Nippon Seiko Steering Gear:

The pitman arm is rigidly connected to the outer end of the sector gear shaft. Between the ball nut and the worm, Fig. 1, is a row of steel balls, which serves two purposes: to provide rolling contact between the ball nut and worm shaft and to keep the ball nut engaged with the worm as if the two were threaded together. With the nut prevented from turning, the rotation of the worm causes the nut to move up or down the shaft.
The worm shaft is an extension of the steering shaft. As the steering wheel is turned, the steel balls roll along in the groove and the nut moves up or down. The steel ball that has reached the end of the groove in the nut enters the return guide. The guide sends the ball back to the other end of the same groove and the row of balls recirculates. The nut then turns the sector gear which turns the pitman arm.
This steering gear is a precision machined unit, calling for special tools for internal repair. The unit should be replaced instead of being repaired.