get drill .. drill hole into lower casing slowly .. get all oily .. tap out a thread get bolt and refit .. refill with some oil .. allow to settle .. remove bolt .. get oily again .. all swarf etc should come out .. refill and off you go ..

well thats what i did and it worked ... the theory was that the ally swarf is alot softer than the large metal gears

just remember i aint no tecnical person