tranny noises?

1996 tsi awd.I have a low pitched rumbling kind of noise from the time the car starts in p.d.r.and n. It either goes away or lessens when in drive (have a rather loud 3" exhaust).The car shifts fine in all gears upshifts and downshifts just fine no clunk when it changes gears- it is an a/t.I am sorry this is so long just trying to get out as much info as I can. This noise started before the carrier bearing /drivetrain rattle which is mostly fixed and a different noise(waiting on a companion flange). The guesses so far hve been torque converter but there are no shift problems and I was thinking flex plate or some kind of bearing. The tranny shop that everyone recommends will only recommend a complete tranny rebuild(same as my durango that was only a cable adjustment) Just trying to see if anyone had a problem like this or any experience or ideas before I get shafted yet again by a "reputable" tranny shop.Live in Maryland would also take any ideas of someone reputable in the area to take it to. Thanks in advance to anyone that can help any pictures that anyone has would be welcome as well.