my question would be, why even change the differential fluid? shouldn't have to and it's a much bigger pain in the ass to do then it's worth...but yes, idiots typically round the 4 sided drain plug off so you can't get it out any longer. It's a classic problem...the old diff plug..what I have seen is that folks take the bottom plug out, via whatever means, drain the fluid and then discover that the filler plug won't come out, the one on top, so they can't refill the damn thing...either way you/they are screwed....I wouldn't even mess with the differential fluid...if the thing goes it goes....and you replace the entire diff.....best of luck
Read it on PelicanParts.com Pelican Technical Article: BMW E30 3 Series Differential Oil Change
I done it before it was not hard at all if the filler plug was not stripped. Shifted much smoother after oil changed. Advice for the first timer changing the differential oil, ALWAYS take the filler plug off first then the drain plug. In my case, if I drained the oil first, then I'm really screwed.
actually I think it's an Allen isn't it on the BMW? I may thinking of Peugeot with 4 sided wrench thing, piece of junk Peugeots are...nevertheless....the situation remains the same, take the filler plug off first and then see if the drain plug will come out..that way you won't can't be stranded...good luck..cliff
Sorry it was the transmission filler plug not the differential. Yes you will need to use a 17mm hex bit. If I can't get it off then I can't change the transmission oil, anybody got a solution to this problem?