330d clonks when clutch released and vibrates on idle

my 330d vibrates on idle and makes a annoying vibarating sound from in the dash, i am a mechanic and the engine is sweet as a nut pulls like a train etc and the problem is only on idle. also when i go to reverse it makes a donk/ clunking sound which it also does sometimes when i release the cluth when changing gear, i dont have much knowledge of rear wheel drives i work on vans. it sounds like there is play in something like a diff mount or the prop shaft but i havnt got a clue, is any of these issues something that you can help me with please? thanks, wayne.