Yes does seem like vibration problem is coming from that worn damper. I had to replace mine on my 85 300sd not so much because the rubber was damaged in it but because the 3 bolt holes that secure it were elongated to the point it would not run in round anymore. The reason it wore like that was my secureing bolts at front of shaft were lose. Im pretty sure you can just take the front off if you loosen at your center bearing holder and let shaft drop down as far as it will go should be able to slip it out of the connection then. I do not know if you can buy the dampener I got a whole used drive shaff front+rear. I think some people have installed w/o that dampener do not know how much it helps. I would be concerned as to what made the dampener go bad are your connections tight?