Flywheel/flexplate on autotransmission?

[mobilejo]

I have a 2011 e70 X5 xDrive40d with 40,000 miles. It has a vibration at idle which is strongest in the steering wheel but can be felt in the dash and the rest of the cabin. It also vibrates when driven and held at 1200RPM in any gear at any mph - so long as its at 1200rpm you will feel it. Slightly worse in D or R, but present and still quite bad in P and N. The vibration is there all the time but is worse when the vehicle is warm and is at its very worst after alot of stop start driving like in city traffic.

So far, 3 mechanics (inc. BMW) have looked at the vehicle without dismantling anything and can't see anything that may be the cause - engine mounts 'look' okay, belts and pulleys look okay, exhaust mount and heatshield looks okay, smooth runnigh test on the diagnostic machine passed, no misfire, no CEL, no vacuum leaks, no visible signs of any problem, MAF tested and working fine. Obviously no one will start pulling things apart without being paid for labour.

When coming to a stop, there is a slight metallic buzz sound that can be heard just as the vehicle stops. The same buzz can sometimes be heard when releasing the brake and starting to move off. It lasts only a second or so.

One mechanic said he would start by inspecting the automatic flywheel where it connects to the torque convertor but I have not found a single case of the flywheel on these cars needing replacement. Does this even sound plausible?