New Flex Disk too hard?
 

I had my front flex disk replaced a few months ago. Since then there has been a vibration in the driveline under medium to high load. The tech who installed it checked the driveline for play, looked at the rear flex disk and support bearing. All checked out. Installation was apparently correct as well. They changed out the transmission mount with my permission without any better results. Had another tech check it out and he checked the whole driveline and now suspects the flex disk that was changed is of a harder/stiffer material. I accepted it but am now wondering. Does anyone have thoughts on the problem and the theory of the cause. Is the difference between the front and rear flex (as the rear one was not changed and is technically apparently still good) possibly causing an imbalance? Does anyone think changing the rear flex disk to the same as the front will stabilize the drive shaft given that apparently everything else seems to be ok? Thanks.

did they seperate the driveshaft at the center support bearing? if they did they mat not have it indexed correctly. they are balanced in a specific location, if it is off it will vibrate, or they may have used an incorrect transmission mount, maybe too high or too low?

The cars driveline has to be rolled back and fotrth a few times to self align/settle before tightening the tans mount, center support, and shaft spline cinch nut. This can not be done on a lift that lets the suspension/differential hang..

Double check the center support bearing. I had similar vibes on mine. I replaced both flex discs and the center support bearing AND mount. The rubber was worn in the mount and was not that noticeable. Everything is fine now.