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
Because even the best tuned AWD systems seem to struggle with low traction conditions. They don’t instantly redirect the torque to the wheel with traction. I’m not sure if this is a mechanical/programming limitation, or if ti is that AWD vehicles need a traction control system that is safe and well behaved in normal on-road driving.
In any case, the AWD systems all seem to have some delay. When climbing an uneven hill this delay leads to loss of momentum as the vehicle is climbing. A locked differential transfers torque instantly to the wheel with traction, so it is easier to keep up momentum. But a locking differential often depends on the driver to disengage it for safe on-road driving.
There are a lot of videos on YouTube showing how well different AWD systems do under challenging conditions. Some systems do much better than others. Subaru generally does better than most.
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