I now have a gearbox problem.

Smooth & silky when cold, once warmed up it flares unpredictably between gears, and the harsh thumps are damned near legend. Throttle position doesn't seem to matter: light or hard the problem seems to be the same. All gears selecting, whether in tiptronic or full auto. There are no DTC's showing on a scan.

Full fluid flush just carried out, transmission service instruction reset. The old fluid was black.

Any suggestions, anyone, please?

 

Should have added: stall test of converter gives no problems, stall is about 2000 rpm in forward or reverse, and no odd noises.