hey guys, i had similar problem on my E34 89 model 525i. Not sure just what part i fixed to get rid of the vibration as i had to fix several things at the same time! started with replacing one of my engine mounts as it was broken, replaced the 2 rear pitman arm links and also took tailshaft off and filled the rubber flex mount? (between gearbox and tailshaft) with Sikaflex.
Car drives good now