Have a 57 335i cab 52k miles and just noticed the rear left suspension is squeeking on compression ie going over road humps. Is this a sign something is not correct?
I had a similar issue with my e36 318is, turned out to be the diff mounting bush, also by coincidence had a dodgy rear shock mount which made more of a tapping / knocking noise under compression.
My E60 was squeaking even just getting in and out of the car. Apparently on this model it's a fairly common fault - rear rose joints - and cost about £20 each. I had mine replaced by Quarry Motors about three weeks ago and it's been fine since.