Limited Slip Differential: An introduction

Limited Slip Differential Cut-away model

1885 was the year when the first gasoline powered transportation came into existence. It took years of research and development to produce a motorized mode of transport. Steam engines were a kind of technological wonders back then. For the common man, horse and cart was the only way to go around town. Modern cars are the result of decades of development. Since then, cars have become ever more complex pieces of extraordinary engineering.

One of the essential parts of a motor car or anything on 4 wheels, for that matter is the “differential”. I would urge the readers to please bear with me on this because the later part of this article strays into the technicalities of a Limited slip differential (LSD). First and foremost, why do you need a differential?

A differential serves three main purposes:

It aims the engine power at the wheels.
Act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one last time.
To transmit the power to the wheels while allowing them to rotate at different speeds.

In essence, a differential allows for different rates of rotation while cornering. In a powerful car though, even with a standard differential, if you put your foot hard on the gas while coming out of a corner, the inner wheel loses traction and eventually starts spinning. At this point of time, the outer wheel which has the most grip keeps putting the power down on the road. At high speeds it becomes a perfect recipe for disaster. A clutch type LSD connects the two half shafts together with a clutch pack allowing a limited amount of clutch slip between each side of the axle. This allows for small differences in rotation while cornering, but prevents violent wheel spin from just one of the wheels. Most modern sports cars feature a limited slip differential.

Ferrari goes one step beyond, with what is known as an E-Diff. Basically, this type of LSD uses speed sensors, accelerometers, anti-lock braking system sensors etc. in unison with microcomputers to monitor for any wheel slip. Porsche’s PSD uses electro-hydraulics to control a mechanical LSD.