How Do Differentials Work?
If you aren’t familiar with differentials in cars and what they do, read on as we briefly explain the commonly available differentials and its mechanics that allow each wheel on a car to spin at different speeds.
- To transfer engine power to the wheels while allowing them to rotate at different speeds.
- To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels.
Differentials are easy to understand when it comes to the wheels that are not powered. This is represented by rear wheels on a FWD, front wheels on a RWD, and front and rear wheels on an AWD (full time 4WD) vehicle.
Part time 4WD vehicles are essentially 2WD vehicles and don’t have front and rear differentials, instead are locked together when selected by driver. As the front and rear driveshaft is locked, this allows the front and rear wheels to rotate at the same speed to improve traction. However, this needs to be switched back to 2WD to prevent axle binding.
An open differential always applies the same amount of torque to each wheel. However, depending on the traction, the torque applied to the wheel is only limited to the amount of traction available. So even though the car’s engine is able to produce more torque, there needs to be traction for it to work.
Pros: Affordable and good for most daily driving.
Cons: Power is sent to the wheel with the least traction and opposing wheel only has limited torque that isn’t enough to power out if you’re stuck.
Limited Slip Differential
Limited Slip Differentials (LSD) solve the problem that open differentials have when it comes to transferring more power to the wheel with more traction. LSD’s are mainly open differentials until slip occurs and the diff will transfer power from the slipping wheel to the one that isn’t. There are a few mechanisms that allow LSD’s which are through clutches, viscous coupling, mechanical, electronic, and more.
Pros: LSD’s transfer power to the wheels with traction and yet is able to rotate axles at variable speeds during corners.
Cons: Power is sent to the wheel with traction, but not continuously. In gravel, sand or muddy terrain, the power alternates between the gripping wheels and yet, full power isn’t truly transferred. (A locking diff will solve this problem and is found in more 4WD vehicles)
While the explanations above maybe difficult to visualise, the videos below will definitely help.