Do any of the hard core Bonneville drivers use this stuff? Good results or bad news?

Yes, I use synthetic oil. It was my dad'* car before i got it and he always used synthetic oil. my car has almost 130,000 and the transmition seems to be great no problems. The only thing that i don't like is the cost of the stuff. Plus, once u use it, you really can't go back. I recomend it.

It is strongly reccommended by jr's3800, one of our local tranny gurus, that you do NOT use Synthetic trans fluid in a 4T60 or 4T65! It'* too slippery, and after you realize you have slippage problems, it'* too late. You can't just flush it out and replace it. Run Synth in the engine, but not the tranny. I'm switching over to a synthetic blend for the first time at my next pit stop.

As the Bird man said.

I put synthetic in about 30,000 miles ago and haven't had any type of slippage problems to date. Now I probably don't drive as hard as some of you guys but haven't had any problems.