Audidoody88

Hi there,i have a 1988 Audi 90 Quattro 2.2 5cylinder 10v 5speed manual and my problem is this.I have a noise coming from the transmission at the rear where the propshaft bolts on.When i spin the rear wheel when the car is jacked up there is a metallicy clunking rubbing noise coming from inside what looks like a big rubber thing.I don't have clue what this part is called or if it can be replaced!!Could someone help please.In the picture it is the large circular rubber looking thing to thefront of the propshaft flange.