Rack and pinion steering runs on the gear-arranged to convert the circular movement of the steering wheel in to the linear motion required to turn the tires. It also provides a gear reduction, so turning the wheels is easier.
It functions by enclosing the rack and pinion gear-set in a steel tube, with each end of the rack sticking out from the tube and 
linked to an axial rod. The pinion equipment is mounted on the steering shaft to ensure that when the steering wheel is turned, the gear spins, shifting the rack. The axial rod at each end of the rack links to the tie rod end, which is mounted on the spindle.
Most cars need three to four complete turns of the steering wheel to move from lock to lock (from far to far remaining). The steering ratio demonstrates how far to carefully turn the steering wheel for the tires to turn a certain amount. A higher ratio means you have to turn the steering wheel more to turn the wheels a certain amount and lower ratios supply the steering a quicker response.
Some cars use variable ratio steering. This rack and pinion steering system runs on the different number of tooth per cm (tooth pitch) in the centre than at the ends. The result is the steering can be more sensitive when it is switched towards lock than when it’s near to its central position, making the automobile more maneuverable.
There are two main types of rack and pinion steering systems:
End remove – the tie rods are attached to the finish of the steering rack via the inner axial rods.
Centre remove – bolts attach the tie rods to the centre of the steering rack.
As steering is essential for controlling your car, it’s important to diagnose and restoration any steering problems as quickly as possible.
The chances are your vehicle has rack and pinion steering.
Thankfully, the basics aren’t hard to understand at all: it’s all about turning rotational motion into linear. When you change the tyre, this turns a steering column, which rotates the attached steering shaft and a worm gear known as the pinion. This gear sits on the ‘rack’, a amount of metal with some teeth cut into it. In order the pinion rotates, the rack movements either left or right, based on your steering input.
Power steering adds a device to 1 part of the rack with a hydraulically actuated piston inside. A rotary valve directs hydraulic liquid to either the proper or left side of the piston – based on the steering direction – which applies strain on the piston and reducing the effort had a need to move the rack.
The rack-and-pinion gearset does a couple of things:
It converts the rotational motion of the steering wheel in to the linear motion needed to turn the wheels.
It offers a gear reduction, which makes it easier to turn the wheels.
On many cars, it takes 3 to 4 complete revolutions of the steering wheel to help make the wheels turn from lock to lock (from far still left to far right).