couple of links for you guys

[link=http://www.torsen.com/products/products.htm]TORSEN[/link]

[link=http://www.variloc.com/variloc_theory.htm]VARILOCK[/link] (similar to new Fioroni Tractive4 etc)

plus another link to a page that is helpful [link=http://www.houseofthud.com/differentials.htm]HERE[/link]

plenty of good reading for you there