Rack and pinion steering runs on the gear-arranged to convert the circular movement of the tyre into 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 steel tube, with each end of the rack sticking out from the tube and linked to an axial rod. The pinion equipment is attached to the steering shaft so that when the tyre is turned, the gear 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 move from lock to lock (from far right to far still left). The steering ratio shows you how far to turn the steering wheel for the wheels to turn a certain amount. A higher ratio means you have to turn the tyre more to turn the wheels a particular amount and lower ratios supply the steering a quicker response.
Some cars use variable ratio steering. This rack and pinion steering program 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’s switched 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 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 important to diagnose and repair any steering issues as quickly as possible.
The chances are your car has rack and pinion steering.
Thankfully, the basics aren’t hard to understand at all: it’s 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 gear sits on the ‘rack’, a length of metal with some teeth cut into it. So as the pinion rotates, the rack movements either left or correct, depending on your steering input.
Power steering provides a device to 1 part of the rack with a hydraulically actuated piston inside. A rotary valve directs hydraulic liquid to either the right or left aspect of the piston – depending on the steering direction – which applies pressure on the piston and reducing the effort needed to move the rack.
The rack-and-pinion gearset does two things:

It converts the rotational motion of the tyre in to the linear motion needed to turn the wheels.
It provides a gear reduction, which makes it simpler to turn the wheels.
On many 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).