In the search of more scews the valve gear was removed.
Here some delicate details were removed as preventive step for not damaging them.
Now it was possible to unscrew the cylinder blocks and remove them.
After removing the bottom plate (screws!) at least the mounting screws for the transfer gearbox were visible and acessible.
The the transfer gearbox could be lifted out of the frame.
After removing the last 4 screws the halves of the case could be pulled apart.
And the the guilty part was detected.
There was a cracked spur gear.
Fortunately i had a suitable spur gear im my grab box. This time out of brass; this will never get cracked. The mouting was a quick job for which i used my puller.
But now ...
... the whole loco has to be reassembled
Lutz
P.S.: Competition question: How many scews had to be removed before getting nuts?