I know others have asked some version of this question, but here goes -- I have a 1990 240 wagon with the dreaded grinding sound coming from the rear. Yes -- it sounds like I'm dragging a huge cardboard box under my car. It's worse in the cold (this is MN after all), usually goes away after I drive a mile or two, is better when I turn to the left (and sometimes right) and is worse when I coast (vs. accelerate).

My question is how to tell whether this is a center bearing problem or a rear wheel bearing problem. My local shop already replaced the e-brake shoes, so that's out, and the rear bearing is their next idea. But, from what I read, it could also bear a center bearing. How can you tell the difference?