Rack and pinion steering uses a gear-set to convert the circular motion of the steering wheel into the linear motion required to turn the tires. It also provides a gear reduction, therefore turning the wheels is easier.
It works by enclosing the rack and pinion gear-arranged in a metal tube, with each end of the rack protruding from the tube and connected to an axial rod. The pinion equipment is mounted on the steering shaft so that when the steering wheel is turned, the apparatus spins, moving the rack. The axial rod at each end of the rack connects to the tie rod end, which is mounted on the spindle.
Most cars need 3 to 4 complete turns of the steering wheel to proceed from lock to lock (from far right to far still left). The steering ratio shows you how far to carefully turn the steering wheel for the wheels to turn a certain amount. A higher ratio means you need to turn the tyre more to turn the wheels a particular amount and lower ratios supply the steering a quicker response.
Some cars use adjustable ratio steering. This rack and pinion steering system uses a different number of the teeth per cm (tooth pitch) in the centre than at the ends. The effect is the steering is more sensitive when it is switched towards lock than when it’s near to its central position, making the car more maneuverable.
There are two main types of rack and pinion steering systems:
End take off – the tie rods are mounted on the end of the steering 
rack via the inner axial rods.
Centre take off – bolts attach the tie rods to the center of the steering rack.
As steering is essential for controlling your car, it’s vital that you diagnose and repair any steering problems as fast as possible.
The chances are your vehicle has rack and pinion steering.
Thankfully, the fundamentals aren’t hard to grasp at all: it’s all about turning rotational motion into linear. When you change the steering wheel, this turns a steering column, which rotates the attached steering shaft and a worm gear known as the pinion. This equipment sits on the ‘rack’, a amount of metal with some teeth cut involved with it. So as the pinion rotates, the rack moves either left or right, based on your steering input.
Power steering provides a device to 1 aspect of the rack with a hydraulically actuated piston inside. A rotary valve directs hydraulic liquid to either the proper or left aspect of the piston – depending on the steering direction – which applies strain on the piston and reducing the effort needed to move the rack.
The rack-and-pinion gearset does a couple of things:
It converts the rotational motion of the steering wheel into the linear motion had a need to turn the wheels.
It offers a gear reduction, making it easier to turn the wheels.
On most cars, it takes three to four complete revolutions of the tyre to help make the wheels turn from lock to lock (from far remaining to far right).
