I have been going round and round with a terrible vibration in my 58 rearend. Finnaly came to the conclsion that after tearing into it about 5 or 6 times that I would just find another one.The vibration always came just as I went to third gear and started to get around 35 or 40.Put the new rearend in and had the same exact problem.But this time I said I would just keep on pushing it until it broke.After about 30 yards of being in high gear it stopped.Went back home and came back the same way and it did it again exactly the same.There was a 30 or 40 yard stretch of asphalt that was severly cracked and loose. It was the roadway. In my 60 plus years of doing my own auto repair I have never felt so stupid but happy. Now I have 2 perfectly good rearends and this time I didn't have to listen to my wife say. ("YOU NEVER LISTEN")