Last year I had what I thought was bearing squeal when I let off the gas coming to a stop with the engine idling, at about 2,500 miles. Took it in to the dealer for what I thought would be a warranty fix.
Turned out that the shroud had gotten banged on a parking stop a few weeks prior (I remembered the thunk) and had been pushed up against the transmission. It took a couple of weeks for the paint to wear through, and for the metal-to-metal contact to make noise as the engine shifted slightly on the mounts.
Dealer didn't charge for the diagnostic time - it was up to me to pay them or do-it-myself, at the mechanic's suggestion.
Just unbolted the shroud (not loose - just bent) and straightened it out - no more noise.