Yeah, I thought of that too, Larry. I hesitated in getting under whilst the wheels were going so fast. The vibes are certainly faster than anything associated with wheels or axels. (I had recently replaced the axel units also.) I'll jack her up again and support with substantial stands, block the front (which would probably be silly to expect security at 45MPH--- maybe chain her up to a big tree ), i'm thinking that the renewal of the center bearing support may have changed the angle of the shafts ever so slightly and affected the discs some.

The extra amplitude at about twenty under acceleration might suggest load-dependant factors since it doesn't do it to as great a degree if under a slight load. The only parts that would be stressed so would be the u-joint and the flex discs. I hardly think that the splined coupling is out of whack although if loose, it could be a definate suspect. Something is giving me fits under there and it gets my attention everytime I drive it.

Is there an anticipated lifespan on the flexdiscs? This is a 1980 w appx 200M miles.

I appreciate the input.