What Are the Different Types of Car Differentials?

car differential

Car diffs have become increasingly complicated over the years, evolving to meet the needs of more powerful and refined vehicles. The three most common types of car diffs are the open, locked, limited-slip, and torque vectoring differentials.

What is a Car Differential?

You might be thinking – what is a differential? In simple terms, car differentials use specialised gears that allow two wheels connected to the same axle to rotate at different speeds.

The primary purpose of differentials is to allow cars to turn corners effortlessly. When your car travels around a corner, the outside wheel must spin faster than the inside wheel as it has more ground to cover.

Your differential achieves this by distributing the amount of torque evenly to both wheels, which permits them to react to provide traction or react to resistance. The wheel with the largest amount of resistance will rotate less, and the wheel with the least amount of resistance will rotate faster.

The History of Car Differentials

Before the invention of automobiles, wagons, chariots and carts all suffered from the same issue being one of the front or rear wheels 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 mounted on the same axle to rotate independently of each other?

The earliest models of cars didn’t know how to approach this dilemma, and they simply powered each wheel on an independent axle. Having two sets of front and rear differentials 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 from which all other differential systems are derived.

The Different Types of Car Differentials

What is an Open Differential?

The oldest and most common design is the open differential, as it's simple and reliable.

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

This set-up is perfectly suited to most production cars. The only weakness is that when only one wheel begins to slip, all power is essentially sent to the wheel with the least traction. This makes the open diff not ideal for off-road driving or high-speed racing.

Open Differential Advantages:

  • Its basic design means it's relatively cheap to produce and purchase

Open Differential 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. A locking differential is almost identical to an open differential in design and function. It still distributes the engine torque between the two wheels equally like an open differential. 

The main difference is that locking differentials 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 one wheel loses traction. This means 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.

Locking Differential Advantages:

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

Locked 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 be 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 that automatically locks the axle's left and right sides together when a spinning wheel begins to lose traction and slip.

For obvious reasons, the limited slip differential is often the car diff of choice for high-performance vehicles, vehicles that tow heavy loads, and drag racers.

Limited Slip Differential Advantages:

  • Automatically locks when slipping occurs

Limited Slip Differential 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?

A differential with torque vectoring represents the latest advancement in car diff technology. Torque vectoring diffs involve a complicated array of sensors and electronics to gather data from the vehicle’s steering system, throttle position, and road surface.

The diff can then distribute the optimal level of power to each wheel according to this data. The torque diff can provide maximum traction while cornering, considerably increasing performance.

Torque Vectoring Differential Advantages:

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

Torque Vectoring Differential Disadvantages:

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

Caring for a Car Differential

The humble car differential is a component few pay attention to during regular maintenance. It’s neatly tucked out of sight, doing its job flawlessly – until it doesn’t.

When you consider how integral a car diff is to the functionality of any vehicle, it becomes immediately apparent why it’s so important to keep it in tip-top shape. After all, without a car differential, your vehicle would not be able to turn effectively.

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. 

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

As with any component in a vehicle, regular servicing equals optimal performance.

Its highly complex nature means that a car transmission specialist should complete any maintenance work. However, learning the warning signs of car diff problems can allow you to take action before any real damage occurs.

If you encounter any of these, have your differential serviced as soon as possible:

  • A whining noise when accelerating
  • A whirring noise when decelerating
  • Rumbling at the steering wheel or a whirring sound when you exceed a certain speed
  • A regular clanking sound, which repeats every metre or so
  • A banging sound when turning a corner
  • Rumble while turning may indicate worn wheel bearings
  • A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft
  • Clunking when starting to move or getting on/off the gas might be loose yokes, bad u-joints, a worn transfer case or transmission parts

Contact the Differential Experts Today!

Your car or truck won’t be able to get too far without the ability to turn. For differential and car 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) 9025 3214!