727 tf slipping when cold

Hi

So I recently changed the the shifter from a home-made thing to a B&M cable. I also changed the oil and filter while I was at it. Now the car needs al lot of RPM to barely move when its cold, and the shifting is really wierd. Like suddenly shifting to neutral while driving, then back again.

It gets better as the temps rise, but never 100%

There is no kickdown cable, I have a lokar lying around. To begin with the bolts that holds the oilpan was tightened, but after a short drive I had to tighten them more. This seemed to make the problem slightly better after re-tightening. Now they are as tight as they will go though.

No oil is leaking, but at one time, while driving, there was a slight "puff" of smoke, smelled like hydraulic oil.

So any ideas? Wrong filter install? To much oil? Need the kickdown cable?
Not the most time to spend in the garage these days, but I can not get this problem out of my head.