Automatic Transmission - 4L80E converter locking up in reverse

Just completed my 4L80E transmission swap, transmission has been locking up (what feels like locking up) in reverse and also when coming to a stop (below 5mph). It acts like a manual trans and engine tries to stall.

This happens once the transmission temp reaches approx. 160 degrees, below this temp there is no problem. I bought this transmission from a friend and he had a rebuild about 2000 miles ago and worked fine when he pulled it out.
The only change i made was a filter change and a new Circle D triple disc converter.
I have done data logging and it does not show converter being engaged. The force motor shows 0.10 amps and 96% line pressure when this happens. Once stopped the car is fine as soon i put it back in reverse and move it, it engages again.
I had Bill at Hp tuners do a segment swap, i am using Speartech wiring harness so no wires have been cut. I have done searches and found other people have had the same problem, but no one ever posts what the fix was.
I am at a loss on how to fix this any help would be appreciated.
Thanks in advance.

Still looking for ideas

I was hoping some sponsors would chime in, they must of heard of something like this before.

The lockup circuit doesn't get pressure until the trans shifts to 2nd, so there "shouldn't" be pressure for the converter to lockup in reverse.

You have a crossleak, converter issue, issue with the valves in the pump (stuck) or other internal issue.

I have seen it happen on the dyno with a pump and we couldn't find the actual cause. All valves moved fine, looked ok on teardown, pump halves were flat, everything looked perfect, but it would run in lockup in all gear ranges. A pump replacement fixed that unit.

The lockup circuit doesn't get pressure until the trans shifts to 2nd, so there "shouldn't" be pressure for the converter to lockup in reverse.

You have a crossleak, converter issue, issue with the valves in the pump (stuck) or other internal issue.

I have seen it happen on the dyno with a pump and we couldn't find the actual cause. All valves moved fine, looked ok on teardown, pump halves were flat, everything looked perfect, but it would run in lockup in all gear ranges. A pump replacement fixed that unit.
Thanks for the info.

As stated above, look at the valve body or pump and you will find the problem most likely! Good luck to you!

As stated above, look at the valve body or pump and you will find the problem most likely! Good luck to you!
Thanks for the reply.

I know this thread is dead but I'm having exact same issue! I'm not sure if its valve body or pump. Do you guys think its worth a shot to change the valve body or go straight to the pump?

Op, what did your problem end up being?

I know this thread is dead but I'm having exact same issue! I'm not sure if its valve body or pump. Do you guys think its worth a shot to change the valve body or go straight to the pump?

Op, what did your problem end up being?

What converter?

I'm on the stock 4l80e converter. It still seems to function well in driving conditions, and lock up good.