This is probably a long shot, but does anyone know the thread size for the studs on the lower motor mount? My old mount was worn and needed replacing anyway, but I noticed when I removed the nuts they were pretty loose. I put a new one in about 5 months ago, and I'm just now hearing a subtle clunk again when shifting into reverse. I'm willing to bet they've started to loosen over time, granted I MAY not have tightened them down enough the first time. If I remember they were just plain flange head hex nuts, seems to me a nylock nut would be a better choice given all the vibration being transmitting to the mount.