Worn diff bearings can be often diagnosed by a shaking speedo needle under torque. If it's the main shaft bearing, then the shaft is propably fucked too. This leaves at least these options:

Part with some cash and get a bullet proof box from Bernie.

Buy any used box and hope it lasts.

Buy a used box and swap the diff for the LSD form your old unit and while having the box open, change the bearings as well.

If the main shaft is not yet FUBAR, you can use a larger IB5 gearbox bearing with a separate inner race. This requires the casing to be machined sligghly and this can be done over here for around 50-100e. None of these conversions have yet broken down to my knowledge. (knock on wood)


There was a good topic on S2 gearbox repair some months ago. Try searching for it as it might help.