hi , i have a 59 plymouth belvedere 4 door . when travelling between 30 - 60 ks it has a severe drive line vibration !almost like a shudder, has anyone encountered this  before or can any one steer me in the right direction . i read some time ago that it may be the engine mounts installed the wrong way around , is this possible?? any help would be greatly apreciated  

You post driveshaft vibration, did you check u joints? you probably have a trunnion joint. process of eleminiation. r&r these. Is this a sudden occurence? Did you run over something recently? You may have tweeked the shaft, lay a good straight edge around the shaft. Did you recently put new tires on the back? could be balance issues. axel u bolts tight?  

hi , the uni joints are fine and i checked the tailshaft with a straight edge and its all fine , its got me stuffed!!  

What`s the history of this car? have you driven car for awhile, and this is a sudden occurence? or did you just buy car? you mention engine mounts. did you or someone pull engine, or tranny? If automatic, did you replace converter?  

I know you said that you checked the shaft, but if it does have a trunnion joint on the front of the shaft, you cannot check it in the car.  Take the shaft out and take the trunnion apart and check it for damage or wear.  Check the reg u-joints by taking off the caps and inspecting them.  If there is any sign of rust (look at the u-joint caps where they meet the T joint) replace any suspect joints.
Don