Its behind a 406 sbc with some nasty flowing heads 335 cfm and big solid cam. Its got TVmadeEZ.com's carb plate and throttle linkage arm and the setup has all been accomplished per their instructions. Trans shifts fine all day long and you'd never know this problem until you go WOT. Fluid level is fine, has a shift kit and corvette governor (6300-6500 rpm). Any help is greatly appreciated.

 

You might be hitting the rev limiter before the trans is ready to shift.

 

My msd box has a 7k chip in it and it should be shifting @ 6500 w/ the corvette governor.

 

I have the same problem with Raptor TH700 behind a ZZ383, my msd box has 6k chip and the transmission should shift at 5500. It shifts fine from 1-2 but not from 2-3 I heard it might be a cable problem, havent had time to look at it yet.

 

I was having the same problem. It would shift fine from 1-2 but it wouldn't shift at all from 2-3. I pulled the trans out and tore it apart and put a transgo shift kit in it, the kit was to make it full manual. When I tore it down it had a seal out for a set of clutches. The trans would shift fine in plane driving. The transgo kit didn't help much, it actually made it worse. The easiest way I found to solve the problem was to put a manual in the car, haha.