I wondered about the coupler, it seems like when that's the issue it's sound like gravel banging around in their at idle? I listened to some videos and mine seems ok at idle. I don't think it has been rebuilt, have the last 100K worth of receipts. Can get a recording of it at idle, may be a bit before I can get it somewhere I recreate the vibration. Was going to the last time it happened but by the time I got my phone out I was already over the hill