93 Duster 2.5L with hard 'wobble' when stopped but in gear!

I have 130,000 miles on this car but it is in generally good shape. But, I have this heavy wobble sound, not a thunk, no striking or grinding, just like something spinning is off balance like a washing machine. It doesnt happen in park or neutral, only in gear, and only if I am not on the gas. It is much stronger if I am stopped like at a light, waiting to go. Take my foot off the break and it quiets down, start to drive and it is virtually gone. Is there something off in my transmission? (Automatic) Some months ago a very reputable shop (ASE Blue star and AAA recommended) had to change out the flywheel as it had spun out the center from rest of it and subsequently ripped up the timing belt. (think of the flywheel as one large disk with a hole in the middle, then having a 6 or 7 inch circle sawed out of the middle of it). Any ideas? Has something come loose in the work they did?