I finally got around to changing the center bearing on my 85'300D turbo with 165K miles on it. The bushing around the bearing was completely shot allowing the drive shaft to move at least a half inch in any radial direction. I carefully marked the shaft halves and the flex disk yokes on both the transmission and differential ends. After re-installing the shaft with new flex disks, I took it for a test drive. I now have a major vibration from the shaft starting at about 55 mph. Interestingly enough, the vehicle didn't have any noticeable shaft vibration prior to my replacing the center shaft bearing

. I'm dumfounded on what to do next. Is it possible that the new flex disks have created an imbalance in the rotating assembly causing the vibration? Any help on this subject would be appreciated. Thanks!