Jeep Strokers

I bought a 4.5L for my WJ (I know, next time I will go big) and I have the POS 42re. Well, I rebuilt the transmission myself. Basically I just replaced the clutch plates and seals and added a shift kit to the valve body. Now when I really hammer on the throttle and it kicks down I lose the transmission at around 4,00-4,500 rpm. If I just accelerate and a good even pace it works as advertised.
So the question is: does anyone have a clue where I should start looking to find out wtf I did?

Thanks in advance.

Nothing wrong with the 42re if properly built.Its basically a 904 which guys have been racing for years.Did you take the check ball out of the cooler line?Most have them where the lines connect up by the radiator.If its still there just drill it out and make sure you clean it out really well after.Also did you check the level in neutral?Dont check it in park.Ive found these are very picky on the fluid level,they will suck air if even a little low.I usually run mine about a half quart over filled.Is the tv cable properly adjusted?It controls line pressure and will change shift points slightly.Let me know how you make out.

The level is good in neutral. I will check on the rest. Thanks!