Passat b6 knocking

Hi guys, a quick question about something that has been irritating me for around a year now. I have a 2006 2.0tdi and when driving at over 40 mph I get a kind off tap tap tap . If I put a little pressure on the clutch you really can feel the tapping. If I take the car out of gear the tapping goes. If I rev the engine whilst stationary no tapping. I figured it might be a worn spline on the driveshaft? Anyone have any ideas?? I’ve taken it to the local vw dealer 3 times and they can’t find anything.

Just got her back from the mechanics after 30,000 mile service… They still couldn’t find the problem

Sounds to me like either a clutch assembly problem or something “down the line”, that only taps when under load, like a CV joint.

Does turning make any difference?