I'm relatively new at MB maintenance, but as I run into new problems, I'm learning. My 89 300se is having a vibration problem and have been told that I should replace the driveshaft support bearing and the flex discs. I have a couple of dumb questions. Are the front and the rear flex disc different or are they interchangeable? Also, not being a mechanic, I don't know what the purpose of a flex disc is. Any help would be appreciated.