Nothin but a Ford

Ok, lots of views on flexplate differences, but no input. So how about this one. How can I be sure it is a cracked flexplate. I have read where it normally rattles out while idling. Mine only makes noise under load, and is smooth and quiet otherwise. Most say that it sounds like a bunch of tin cans or your muffler dragging behind you. This is more of a hollow sound like a big pressure washer before the pump kicks out. Some say converter, but I have changed the fluid, and filter, and there were no shavings. I have heard about the starter drive striking the ring gear, and there was also mention of the timing being off, and it being detonation. If that is the case, I have never heard sparkknock like that before. I did notice that when I drained the converter, that the weight on the flexplate closest to the crank rubs on something, could I have too much endplay in the crank....Does the crank tend to walk forward under load, or back. I hate to pull the tranny, and have no crack. Any thoughts