What is a Differential and what does it do?

The differential was actually patented in 1877 by James Starley, a builder of bicycles and a self-taught genius of the industrial revolution. In due course, a company created by his nephew, James Kemp Starley, gave rise to the [Rover] car company.

The main function of a differential is to allow wheels to turn at different speeds while receiving power from the engine.

Consider your wheels when negotiating a turn. Your wheels on the outside of the turn have further to travel so turn at a faster speed.

If the wheels were connected using a solid shaft they would have to slip to compliant the turn.

That’s where your differential comes in. Allowing the left and right wheels to turn at different RPM (revelations Per Minute) while transferring power to both wheels.

Apart from allowing the wheels to rotate at different RPM the differential has two more functions.

First is speed reduction at the pinion-ring gear assembly. This is achieved by using a ring gear which is having almost 4 to 5 times number of teeth as that of the pinion gear. Such huge gear ratio will bring down the speed of the ring gear in the same ratio. Since the power flow at the pinion and ring gear are the same, such a speed reduction will result in a high torque multiplication.

The other function of the differential is to turn the power flow direction by 90 degree.

The differential we have gone through so far is known standard differential. It is capable of turning the wheels at different rpm, but it has got one major drawback. Consider a situation where one wheel of the vehicle is on a surface with good traction and the other wheel on a slippery track.

In this case a standard differential the majority of the power will be sent to the slippery wheel, so the vehicle won’t be able to move.

A full-time 4WD vehicle also has a centre-diff’ in the transfer-case because the front wheels rotate more quickly than the rear ones when turning a corner and travelling forwards.

Engaging the centre differential will provide drive to both the front axle and rear axle.

Only engage diff lock on loose slippery surfaces where extra traction is required. NEVER use diff lock on high traction areas like the road. Unnecessary wear will occur to tyres, transmission, universal joints; this is known as transmission wind up and puts many mechanical components under unnecessary strain. Steering will also become stiff.


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