In a manual recirculating ball steering gear, the steering column input shaft connects to a worm gear inside the box. The worm gear acts like a screw and moves a ball nut back and forth. The ball nut has teeth on one side that rotates a sector gear attached to the pitman arm. So when the driver turns the steering wheel, the worm gear inside the box slides the ball nut one way or the other. This rotates the sector gear which moves the pitman arm to work the steering linkage and turn the front wheels.
Ball bearings are used to reduce friction between the ball nut and worm gear. The balls roll in a series of grooves between the ball nut and worm gear. Each ball pushes the next one along until they reach the end of the path. A return tube then carries the balls back around the outside of the ball nut so they can reenter the grooves from the opposite end. This creates a continuous loop of balls as the worm gear turns. That’s why they call it a recirculating ball steering gear.
To further reduce friction, manual steering boxes are filled with a light viscosity grease (gear oil or ATF should NOT be used). The lubricant requires seals on the input shaft and pitman arm shaft. These seals are prone to leak after many years of service, which causes a loss of lubricant and accelerates wear inside the steering box. Overfilling the steering box with grease (it should only be about 2/3 full) may create too much pressure inside the box and force out the seals.
|
