dude, dont be alarmed, i have an act flywheel as well, as well as a stage 2 act clutch, that is currently being replaced (seriously hands are still dirty). It has to be the flywheel, i even dropped my tranny to try and tighten the flywheel, I THOUGHT IT WAS LOOSE. But the torque was correct on all the bolts and it still does it to this day. The transmission was also replaced a year ago, that when all the parts went in, its started to make that soft grind after the new install but trust me... its RIGHT!! It might not be too healthy but its right!