Does anyone know someone reputable that makes a true performance 4T80E? I havent seen one no matter where I look. Also, who knows an LSD maker? Didnt Mark get his from yank along with the beefed converter?

the only place i know of is IPT. heres the link http://www.importperformancetrans.com/gmautofwd.shtml

Engineered Performance built the LSD for Mark http://www.engineered.net/

There's a play in Harriman, NY that built performance GM FWD transmissions. They said they have done a few 4T80 E's, but they only build them in house. http://www.engineered.net/

Ok cool thanks. I am just doing some homework as someday the tranny wil be sent to trans heaven. When I do replace it though I want an LSD and a bulletproof trans like the sites above would have. The parts IPS uses looks good. That thing would probably shift great. Not sure I would want a 3800 stall like Mark though, thats a lot of extra slipping so you would need a external cooler. I would just look for maximum reliability and performance, and that calls for the above mentioned (LSD(definately) and built trans)

you could go with something a little less radical like 2800rpm and still see a significant increase in performance. That's he size Mark originally had in his car.