4L65 not engaging

[HwyStarJoe]

I'm out of ideas and would love some pointers on this issue.

Swapped an '06 GTO LS2\4L65-e into my '69 Camaro and I'm having trouble getting the trans to respond.
The TCU has 12v on Pin 31, and the TCC signal is connected to the brake light switch.

The dipstick reads fluid at the Cold area while checking it at idle in Park. I filled it with Dexron VI and run it up and down the driveway shifting through all of the gears.
It acts like a trans that doesn't have enough fluid. The engine and trans have never come apart from each other so whatever fluid was drained either dribbled out the tail, or was dumped when I did the filter change. The cooling lines have never come off either, and go to a stand-alone cooler.

It moves in Reverse fine. In all other gears except maybe 1, it's sluggish as though it doesn't have enough fluid. In 1 I can actually feel the trans shift and the car moves somewhat responsive but still not as it should.

My ODBII scan software is only a basic version and won't show me the TCU. But I am getting a U0101 Lost Communications With TCU code. I don't know if this is because my scanner won't read it, or because there's an issue with the TCU. I have the full GM software package coming which should tell me one way or the other about the TCU.

Any ideas why the trans is acting this way?
Thanks all