Rack and pinion steering uses a gear-arranged to convert the circular movement of the steering wheel in to the linear motion necessary 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-set in a metallic 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 so that when the steering wheel is turned, the apparatus spins, moving the rack. The axial rod at each end of the rack links to the tie rod end, which is attached to the 
spindle.
Most cars need 3 to 4 complete turns of the steering wheel to go from lock to lock (from far to far still left). The steering ratio demonstrates how far to turn the steering wheel for the wheels to turn a certain amount. An increased ratio means you should turn the tyre more to turn the wheels a specific quantity and lower ratios give 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 effect is the steering is usually more sensitive when it is turned towards lock than when it is close to its central position, making the car more maneuverable.
There are two main types of rack and pinion steering systems:
End remove – the tie rods are attached to the end of the steering rack via the inner axial rods.
Centre remove – bolts attach the tie rods to the center of the steering rack.
As steering is essential for controlling your vehicle, it’s vital that you diagnose and repair any steering problems as quickly 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 turn 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 length of metal with some teeth cut involved with it. In order the pinion rotates, the rack movements either left or correct, depending on your steering input.
Power steering provides a device to 1 aspect of the rack with a hydraulically rack and pinion china actuated piston inside. A rotary valve directs hydraulic fluid to either the proper or left part of the piston – based on the steering direction – which applies strain on the piston and reducing your time and 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 into the linear motion had a need to turn the wheels.
It offers a gear reduction, which makes it easier to turn the wheels.
On the majority of cars, it takes 3 to 4 complete revolutions of the tyre to help make the wheels turn from lock to lock (from far remaining to far right).