Ok, after reading tons of this thread, I may have a coupler worn. I just heard it today at idle, and my engine was warmed up. It indeed sounds like a rock tumbling party, not loud but distinct. My question is, does this tend to also create an electrical "smell"? Haven't checked the oil yet, just wondering if this smell should be a concern or is just associated with a worn coupler?? I don't think it's an alternator bearing, but I could easily be mistaken.