I have a 1998 323i coupe which has for some time been making a whirring noise which increases when I speed up and decreases when i slow down. This has recently got much noisier and is sometimes accompanied by a rattle. I am told it is a noisy diff and it is a common problem. If its that common I wondered if anyone else had encountered it? Ideally I would replace it with a reconditioned part but as this is likely to have come from a car even older than mine is it likely to just happen again?? Any help appreciated.