Saginaw Rack & Pinion Gear

Fig. 1 Exploded view of rack & pinion gear:

The power rack and pinion steering system, Fig. 1, has a rotary control valve which directs hydraulic fluid coming from the pump to one or the other side of the rack piston. The piston is attached to the rack. The piston converts hydraulic pressure to a linear force which moves the rack left or right. The force is then transmitted through the inner and outer tie rods to the steering knuckles, which turn the wheels.
If hydraulic assist is not available, manual control is maintained, however more steering effort is required. The movement of the steering wheel is transferred to the pinion. The movement of the pinion is transferred through the pinion teeth, which mesh with teeth on the rack, causing the rack to move.