1987 325e Driveshaft problem

I own a 1987 325e. I have a serious vibration and clunking sound coming from the driveshaft. This car has 4 bolts (all the manuals show 3 with a guibo) that connect the drive shaft to the auto/tranny and no guibo! (I also own a parts car, same year and model, with the same setup and it ran well before I killed it!) I went through two center bearings already. Could I have a bad drive shaft, differential, tranny or what?