Rack and pinion steering uses a gear-set to convert the circular movement of the tyre into the linear motion required to turn the tires. It also provides a gear reduction, so turning the tires is easier.
It works by enclosing the rack and pinion gear-established in a steel tube, with each end of the rack protruding from the tube and linked to an axial rod. The pinion equipment is mounted on the steering shaft to ensure that when the tyre 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 attached to the spindle.
Most cars need 3 to 4 complete turns of the tyre to move from lock to lock (from far right to far still left). The steering ratio shows you how far to turn the tyre for the tires to turn a certain quantity. An increased ratio means you need to turn the steering wheel more to carefully turn the wheels a specific quantity 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 teeth per cm (tooth pitch) at the heart than at the ends. The result is the steering is definitely more sensitive when it’s turned towards lock than when it’s near to its central placement, 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 vehicle, it’s vital that you diagnose and repair any steering issues 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 switch the steering wheel, this turns a steering column, which rotates the attached steering shaft and a worm gear referred to as the pinion. This equipment sits on the ‘rack’, a amount of metal with a series of teeth cut into 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 part of the rack with a hydraulically actuated piston inside. A rotary valve directs hydraulic fluid to either the proper or left side of the piston – depending on the steering direction – which applies pressure on the piston and reducing your time and effort needed to move the rack.
The rack-and-pinion gearset does a couple of things:
It converts the rotational movement of the steering wheel into the linear motion needed to turn the wheels.
It provides a gear reduction, which makes it easier to turn the wheels.
On the majority of cars, it takes three to four complete rack and pinion china revolutions of the tyre to help make the wheels turn from lock to lock (from far left to far right).