What is the advantage of a locking differential?

Question

I was looking into going on some light off-road trips in my new car, and while browing related info, I ran into this a lot: that all serious off-road vehicles require a locking differential.

My understanding of the locking differential is that the differential can be locked, meaning the left and right wheel are required to spin at the same rate. That is useful for situations where one wheel might not have traction, which would normally (without locking differential) cause it to spin and get the most torque. Locking differential prevents this by forcing both wheels to spin at the same rate, preventing the no-traction wheel from getting all the available torque. This much, I think I understand.

What I don’t understand is, how is that better than a traditional AWD system, where the car can decide which wheel gets the torque? In my mind, this is even better because as soon as the car detects loss of traction, it will cut the torque, achieving basically what the locking differential does without the downsides (like worse corner handling). For example, my new car, a Subaru Outback, supposedly comes with this kind of AWD system that can distribute torque as needed.

So my question is, why is a locking differential better than just having a normal AWD?

In: Technology

Answer 1

First of all, poor cornering is not a “downside” of a locked diff amy more than poor acceleration is a downside of breaks, because you’re not meant to have your diff locked when you’re cornering. As in, you’re going to be told that in the user manual, don’t have your diff locked in normal operation.

Locking the diff is meant for the harshest of off-road situations, where some your wheels will often loose all of their traction, either by spinning mid-air or in loose soil/mud/snow. With a locked diff, you do not lose any torque on spinning wheels with no traction, instead those with traction get full power at all times. This makes it possible for the vehicle to get out of a situation that it otherwise might get stuck in, even with computer controlled AWD.