Help with unusual sound only when freezing
 

I have a weird almost moan coming from my 1997 328ic whenever outside temperatures dip. When going slow, it sounds like a clicking and as I go faster, it turns into a moan.

It is definitely speed related and seems to have nothing to do with the engine. I can feel it in the gear shift (I have an automatic), and it does not go away when I put the car in neutral (while rolling). Braking doesn't seem to affect it (aside from the speed of clicking changing), so I guess it's not the brakes.

It goes away after 5 - 10 minutes of driving (warmed up I'm assuming?). I only notice it while cold and the ambient temperature is cold. I never notice when it's 50 degrees out.

I'm just looking for any ideas as to things to look at.

The only things that it could be based on your description, is the Tranny, center support bearing, the differential or a wheel bearing.

You may be able to isolate the Tranny and center support by running it, in the cold, with the car off the ground.

I doubt it is the wheel bearing based on your description.

My guess is it is the tranny. I would replace the tranny fliud with the proper type, probably ATF, as my first step.