How in the world do they work? Every scenario I run through in my head comes back to a series of magnetically activated clutches with a preset amount of slip based on how much power you want to go where (50/50, 60/40, 30/60, etc). So if that is the case I just can't see one holding up very long at all. So how do these damn things work? And how does it know if the power is distributed as intended?