190e not upshifting from 3rd? Possibly empty torque converter?

[alexku]

Hello all, I am hoping someone can help me with an issue I am stuck on with my 772.4 auto transmission on my 1988 190e 2.6

I recently installed a working transmission from a friends car who preformed a manual swap, I installed it, had some issues with gears activating which was fixed after pouring through a lot of fluid and disassembling and cleaning the valve body.

I now have an issue where the car engages very late at 3000 RPM at (third?) and does not want to upshift from I believe third? P N D R 1-2 work fine and the throttle response is perfect but as soon as I enter third its very delayed and will not upshift despite being up too speed or almost redlining it.

I have checked all the fuses, switch behind gas pedal, and transmission shifter cable on the throttle body which seems to be in tight working order.

Any suggestions to fix? I asked around and did some research and people have suggested the torque converter being empty, defective kickdown solenoid, or defective governor assembly.

Any pointers or suggestions would be extremely appreciated, my next moves are to check torque converter for proper fill level and replace the solenoid.