A “rack and pinion” is a type of steering gear, a device that transfers the rotational motion of your steering wheel to the lateral, side-to-side movement needed to turn your front wheels.
Sometimes referred to as the "steering rack", the rack and pinion assembly is made up of a long metal tube that is mounted between the front wheels. Inside the assembly is housed a long metal rod with teeth cut into one edge - the “rack”. The rack is moved to one side or the other by the “pinion” gear when you turn your steering wheel. Most rack and pinion assemblies also feature an internal hydraulic piston to lend power assist to the steering operation, making it easier to steer, especially when your vehicle is sitting still.
Attached to each end of the rack and pinion is another metal rod called a tie rod. The tie rod extends the rack outward to the components connected to the wheel.
While the rack and pinion type of steering gearbox is not the only gearbox used, it is the style most commonly found on late model vehicles.
The procedure to replace the rack and pinion assembly is fairly involved on most vehicles. The job often requires significant removal and disassembly of a number of other vehicle components, including the engine cradle (subframe) in some cases.
In general, steps to replace the rack and pinion assembly include: