With rack and pinion steering, the rotation of the pinion causes linear motion of the rack, which turns the vehicle's wheels left or right. Rack and pinion systems are a common component in railways. In between train rails are racks that interact with pinions attached to locomotives and train cars to assist trains with moving up steep inclines.
While a rack and pinion system might seem complicated, according to Advance Autoparts, it is simply a gear attached to a toothed bar. The bar attaches to a set of tie rods. A generating rack is a rack outline used in the design of a generating tool, such as a hob or a gear shaper cutter, to indicate the details and dimensions of the teeth. Simple linear actuators often consist of some combination of rack and pinion. The shaft rotation of the pinion is powered by hand or by a motor to create linear movement.
While the rack and pinion steering system has been used by U.S. automotive manufacturers for less than 50 years, the concept is nearly a century old in other countries. Hemmings Motor News reports that in the 1930s, BMW produced the first rack and pinion gearbox. The first American automotive manufacturer to use rack and pinion steering in production was Ford, which used it for the 1974 Mustang II and the 1974 Pinto. While AMC adopted the system soon after for the 1975 Pacer, GM and Chrysler would not manufacture cars with rack and pinion steering until the 1980s.
Although it took some time for U.S. manufacturers to start producing rack and pinion steering systems, they soon realized what European and Asian automotive companies had known for decades. Rack and pinion steering is a more straightforward design compared to the recirculating ball steering system that came before it. That more straightforward design makes rack and pinion steering systems more cost-effective to build.
Hemmings also notes that the rack and pinion steering system weighs less than a recirculating ball gearbox, which helps improve gas mileage. Rack and pinion systems are lighter because they don't require the idler arms, Pitman arms, center links, and tie rod sleeves found in conventional steering systems. The size and weight of a rack and pinion system make it a better fit for front-wheel-drive applications because manufacturers can install it right next to the transverse drivetrain. It is easier for manufacturers to tailor rack and pinion gearboxes to fit specific wheelbases and handling packages.