hey forgot to say hello, when saw your prob first word out of my mouth was crap!
i just went looking across this site and came across some of the old posts regarding the issue, where it was suggested to be an exhaust problem is that still the case? all i get is a Drone at around 55mph, i dont experience any shudder but the drone goes away when i drop to 4th.
55-58 Vibration (1700 RPM) info & part numbers