Here's my busted Differential pictures...

[Hummie2]

Yes,trac control does require wheel spin for it to work. A spinning wheel that suddenly catches traction sends a high shockload to the drivetrain however and thats a shortcut to disaster for these rigs.

Trac control works pretty well, but it won't eliminate all wheel spin. There is a reacation time for it to sense wheel spin and its pretty easy to over power it altogather. I have a front locker in my H2 and very rarely use it because trac control does a pretty job all by itself if given a chance to work. The H3 trac control appears to work as well or better than the H2s, but I think from watching a few H3s they might have a higher RPM threshold for it to sense wheel spin(?).

I still hold my breath everytime I see one spin and I long for the old days when I used to be able to blast through things with all 4 wheels spinning sending mud, pinecones, and bolders flying 100' in the air.

BTW, Bebe check your PM. I finally noticed the question you asked.