Here's what the inside of a working differential looks like
I'll be honest I don't know exactly how differentials work. I understand that they distribute power between wheels and can vary that power input based on driver inputs and the general positioning of the car. Luckily today we get a peek into an actual differential working.
This video by legendary diesel truck tuner Gail Banks explores the interesting world of truck differentials. This test shows exactly what happens inside the casing by using a see-through part.
The most interesting bit of this test is how the differential lubricates itself at speed. I understand that the differential is a metal case full of gears and sometimes clutches filled with differential fluid. I assumed the gear oil arbitrarily flew around the differential case and somehow fell on the gears, but that's not the case.
In watching this video we get an incredible view of how the thick gear oil evenly distributes on the gears and forms a sort of wave around them. Hardly any of the gear oil flies around the case and instead falls exactly where it needs to. Damn those engineers are smart.