I have a stock trans other than upgraded VB. I ran my Smarty on #7 for a few runs before the VB and it seemed to work ok. I put the VB in and tried it on #9 and instantly screwed up my TC at half throttle, it slips in lockup now. One fellow on here has run his on #9 on stock trans for a while with no problems so I might have gotten a weak TC from the factory, but I would suggest no more than attempting #5 MILD on stock trans. That is even probably a bad idea. I suspect #5 MILD with a VB is ok, that is what I am running now and it runs great as long as the TC isnt locked. It is very fast spinning the tires all way to 60mph, so I figure my trans clutches are ok. Smarty #5 MILD + performance VB =