Kirby

I recently got curious as to what broke on my old 10 bolt so I ripped it apart and apparently the internal gearing started to chew up a bit. I've been looking for a temporary fix just to get her running but no Torsen rebuild kit exists. Has anyone besides me ever thought of the possibility of machining new internal gearing made of a higher grade steel? Seems to be a good market for it out there for us close-to-stock A4 guys until funds permit a 9" or S60 upgrade. Mine is my DD so waiting to save thousands for a beefy rear is out of the question. Just wondering if anyone out there has ever thought of doing the same thing or how much something like that might cost.