4l60 bogs on acceleration

4l60 swapped into a 78 TA with an '01 vette LS1. When accelerating from a roll (like turning a corner) and going up a hill, the converter seems like its locking up too soon and RPMs drop so much that I need to shift to D out of overdrive to some power. It only happens when its on a roll, from a dead stop, even flooring it from a dead stop, its ok.

I think the converter is released when I start the roll and accelerate because the car accelerates for a couple of seconds, then it falls on its face. What parameters should be checked? Could it be that its shifting to a higher gear too soon?

Set up an A/T trans log. Drive it and see. Log commanded gear, TCC parameters, etc. If that all looks good you probably have an internal issue.