What Are the Different Types of Car Differentials?


car differential

What is a Differential?

A car differential is a system which transmits an engine’s torque to the wheels. It takes the power from the engine and splits it, enabling each wheel to spin at a different speed. However, you may be thinking, why would the wheels of a car even need to spin at different speeds?

Before the invention of automobiles, wagons, chariots and carts all suffered from the same issue of one wheel dragging or slipping when attempting to turn around a corner. The industrial revolution added a new problem to overcome – how do you allow engine powered wheels which are mounted on the same axle, rotate independently of each other?

The earliest models of cars didn’t know how to approach this dilemma, they simply powered just one wheel on an independent axle. This was far from an ideal solution as the wheels were often underpowered and encountered frequent issues with traction on anything other than firm, level ground. Eventually, in 1827, the French watchmaker Onésiphore Pecqueur invented the open differential, the design in which all other differential systems are derived from.

When your car travels around a corner, the wheel on the inside must spin slower than the wheel on the outside as it has less ground to cover. Your differential distributes the amount of torque evenly to both wheels which permits them to react to provide traction or react to resistance. The wheel which has the largest amount of resistance will rotate less and the wheel with the least amount of resistance will rotate faster. 

What is an Open Differential?

The open differential is by far the most simple, reliable and common design found in most modern-day vehicles.

The powered pinion gear, found at the end of the driveshaft, engages with the ring gear, which then transfers power to both axles through another set of gears. It splits the engine torque into two outputs, allowing the wheels to rotate at different speeds.

In an open differential, the level of torque applied is dependent on the amount of tyre traction. If a tyre loses traction, less torque is applied to both wheels. This is why your car can get stuck if there is mud or ice present under just one wheel.

Advantages:

  • Its basic design means its relatively cheap to produce and purchase.

Disadvantages:

  • If one tyre loses traction, the opposing tyre will also lose its power. For this reason, open differentials are unsuited for performance vehicles or uneven surfaces.

What is a Locked Differential?

The locked, or locking differential, is a variant found on vehicles that primarily go off-road. In design and function, a locked differential is almost identical to an open differential. It still distributes the engine torque between the two wheels equally like an open differential. 

The main difference between the two is that a locked differential can lock in place to create a fixed axle instead of an independent one. Both wheels can be driven at the same speed regardless of whether or not the wheel has traction. This means that both wheels have to be stuck in the mud or ice for you to be truly stuck. However, it also means that jamming a branch under one wheel can often get you unstuck.

Advantages:

  • A locked differential can gain a greater amount of traction than an open differential. 

Disadvantages:

  • Binding can occur when excess torque is built up within the drive train and needs releasing. This happens when the wheels are moving at different speeds and twists the axles. 
  • It can very difficult to drive on high grip surfaces because both driven wheels turn at the same speed. 

What is a Limited Slip Differential?

Limited slip differentials combine the benefits of both locked and open differentials through a more complex design. It utilises an integrated clutch system which automatically locks the left and right sides of the axle together when a wheel begins to lose traction and slip. Limited slip differentials are the preferred differential design for high-performance and heavy towing vehicles

Advantages:

  • Automatically locks when slipping occurs.

Disadvantages:

  • Cannot fully lock up. The system requires a speed differential between the two sides in order to transfer torque.
  • Purely mechanical limited slip differentials are reactive – they don’t begin to lock up until after wheel slip has occurred.
  • Often requires regular oil changes and the clutch is more likely to wear out and require replacing.

What is a Torque Vectoring Differential?

Torque vectoring differentials are comprised of a complex system of sensors and electronics which obtain data from the steering system, road surface, and throttle position. This data is utilised by the torque vectoring differential to distribute the ideal amount of power to each wheel depending on the situation. By producing the maximum amount of traction needed, the torque vectoring differential is incredibly high performing.  

Advantages:

  • Fine-tunes the torque delivered to each drive wheel.
  • Can slow down or quicken the car’s rotation around a corner.

Disadvantages:

  • Heavy, complex, expensive and not fuel-economic.

How Can You Care for a Car Differential?

As with any component in a vehicle, regular servicing equals optimal performance. Differential oil is often used by transmission specialists to lubricate differentials and manual transmissions so they function safely and smoothly. Over time, differential fluid can become dirty and contaminated. Continuing to drive with contaminated differential fluid is risky as it can put unnecessary wear on components. In the worst case scenario contaminated fluid can lead to permanent vehicle damage. 

Signs that your differential may need servicing are:

  • A whirring noise when decelerating your car.
  • A whine or howl when accelerating over large or small speeds. 
  • Whirring or rumbling at speeds over 30km/h
  • Clunking sounds every few metres or when your car begins to move.
  • Steady vibration that increases with vehicle speed.

Plan to have your differential oil changed every 50,000km by a trained technician. Clean, fresh oil will protect your differential and lead to a safer ride.

Getting Your Car Differential Serviced

Your car or truck won’t be able to get too far without the ability to turn. For differential and transmission servicing, turn to Perth’s experts Auto Trans R Us. Contact the Auto Trans team today by sending through an enquiry, emailing us at info@autotransrus.com.au or giving us a call on (08) 9240 5449!