on a 633 csi, complaint of vibration right above 60km/hr (37 mph).
Nasty noise like if you were driving on very bad road.

The rear diff mount was ripping appart the body so we welded that in place.
Still the weird noise.

The center bearing is shot and the driveshaft was moving around (no vabration below 37mph). I am in the process of changing it.

Could it be a bad wheel?? Could it be driveshaft that need to be balanced?

This is a weird one as the car is perfect below 37 mph. as soon as you hit 37 mph and above, you have a bad noise from the back...
As soon as you go right below 37mph everything is perfect again....

Any clues?