It's in a truck, so pulling tailshaft is not all that hard. I can't see needing an additive in a new build, but I dunno. Ohh, running type F trans fluid, which is supposed to be acceptable.
I have kickdown and it functions perfectly, if I were to floor it, the truck jumps into first no problem. Also manually shifting is perfect.
Of note also, I followed Jay's instruction manual and did not install Valve body gasket. I do not think these problems would be caused by that, but figured I'd mention it. With my straight edge and feeler gauges the VB appeared flat.
I do have very good dial type Inch LB torque wrench, so I don't feel I warped anything either.
Thanks for your suggestions, I'll tear into it in the morning and see what I can do.