why does the differential make noise?
Low on fluid, gears and or bearings are shot.
I see in the records, "XX iffylube" changed the diff.fluid. Maybe they didn't use the recommended BMW spec. I should change it out to be sure....
I would take it to a good REPUTABLE European mechanic and have it looked at before you do anything or before you do anymore damage. That's my two cents worth.
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