RACK AND PINION STEERING

The steering gear transfers the rotary motion of the steering wheel to a linear motion used to steer the front wheels. Two types of steering gear are in use today, the standard gear box and the rack and pinion. The standard gear box uses a worm gear that is rotated by the steering wheel to move the pitman shaft. The worm gear contains spiral cut grooves that mesh with a sector gear at the top of the pitman shaft. The spiral action of the worm gear causes the pitman shaft to move the steering linkage in a linear motion. Power steering is achieved by using hydraulic pressure to assist in the rotation of the worm gear.

Rack and pinion steering provides a much simpler method of converting the circular motion of the steering wheel to linear motion for steering. The steering column attaches to the top of the rack and pinion unit and rotates the pinion gear. The pinion gear actuates the rack, which is a simple straight shaft with teeth cut in the top. The rack will simply move back and forth, in a linear motion, in response to the pinion gear. The only steering linkage used is tie rods to indirectly link the rack gear to the steering knuckle. Vehicles with power rack and pinion steering use hydraulic pressure to assist in rotating the pinion gear.