Hello,
I had problems of noise with my transmission box.
I changed all for new parts: gears,axles bearings. nothing to make.
The game of the slipper axle was too important. Maybe the smallest distance (less than a B4 box) between two bearings of the slipper axle is not good for guidance.
Then I decided to cut a part of B4 transmission box and place this part between the plate and S2 transmission box with a bearing.
The guidance of the slipper axle is perfect with this additional part.
Now I must try to validate this modification.
Maybe you have the same problem do you find others solutions?