Hey guys, I've found loads of good information over the years on this site just browsing. I finally had to signup seeking help for a specific problem. I'm working on a 1950 Chevrolet 4 door with a Powerglide and enclosed driveshaft. It has a driveline vibration I can't figure out. It starts around 45 mph and occurs during acceleration, deceleration, and cruising. If I shift into neutral the vibration stops and starts back up again when I shift back into gear. If I keep it in low and wind it up a bit there is no vibration. It only occurs around 45 mph and above regardless of engine speed. I have replaced the u-joint and the bushings and seal in the driveshaft tube with no improvement. Any ideas?