700R4 trans behavior

[kpdalton]

So my truck has the 700R4 trans and it has odd shifting behavior. If I take it easy it drives fine, if I give it a fair amount of throttle it shifts odd and almost feels like the transmission is slipping. Everything is new and rebuilt so I know its not that. I know it needs torque converter lockup kit and the cheapest I've found is $170 at jegs. But from what I read this will only take care of any issues at 40mph or greater & when in overdrive.

I'm wondering if anyone has had this issue and can offer any insight. Its almost embarrassing when its shifting funny which is anytime I try to get on the throttle.