Thanks for the info. Just dropped ours off, took the head tech for a ride, he also acknowledged there was too much driveline noise but says its the 3rd one he's seen doing this. On the first one they saw with this problem they replaced the rear diff, but apparently after 100 or so miles the sound was back, so he wasnt very optimistic about fixing the problem. We drove their loaner x3 which did the same thing (not as loud) and one of the other CPOs on the lot that didn't do it at all. Both similar miles, around 40-45k.

He did say that he would try (again) to present a case to BMW about this problem because he is seeing more and more. Although previously he says they told him that it was normal because so many do it. I'm not so pleased really, not sure what the best thing to do is. This is my wife's car and I don't want her and the baby to have to put up with the whine but for now it is what it is... even so he said he would take a look at it and see if there is anything missing (i think he meant the rubber isolation mounting). I'll post up if he finds anything.

I suspect this issue needs to be taken higher up the chain, somehow persuade BMW to come up with a solution. I'm not sure how this is done though. It really isn't on, a CPO car with a noisy driveline is unacceptable, certainly not what i expect from a BMW, i've had several which i've driven to over 100k miles without serious problems of this nature.