Well today I re-examined the valvebody and B2 and could find no faults, so I put it back together with new fluid. I continued to check vacuum lines, bowden cable, kickdown wire, anything I could see or think of.
I had not driven the car more than 50 miles since this it has started slipping and have changed the fluid for the 3rd time now. I have lost my borrowed car so today I had no choice but to start driving it again.
It slips/shudders at take of, but if done very gently it will make it to any speed I want to go, but again, any sudden throttle increase will induce slip/shudder.
Considering the complete lack of fiber, silt ,chunks or even a burned smell, I am not convinced this 39k trans is shot.

Comments are welcomed