[quotedon't the nascar guys use LSDs? I've never seen one do the one tire fryer when they do their celebratory donuts at the end of the race, and theres always 2 equal, long black marks. although I've wondered that before myself--how can they use a LSD when they're making left hand turns ALL DAY


No they do not use a limited slip perse'. Depending on what you want to call it I guess:
"Regarding the "diff", the only style that can be run per the rules is a "detroit locker" type."
Using the Locker and tire stagger achieves the needed slippage in most cases. http://stockcarscience.com/blog/index.php/2008/04/01/p52