Okay so its like the one in this video? https://www.youtube.com/watch?v=w2bRb17jJ1U

looks like when one wheel slips the fluid heats up and rotates the other driveshaft,
probably helpful on sand and slippery surfaces.
so if i was stuck on ice would 3 wheels spin and one at the front no spin? (example)

for performance applications its an open diff.