[FiftyTwo]

Lots of good suggestions, but I'm leaning towards the torque converter/flexplate area. I thought the torque converter sure looked wobbly as it was running. I'd also like to see a close up picture of the torque converter bolts on the flexplate. Is the flexplate on backwards?

Also, no mention of transmission fluid in this thing. Does it even go into gear? You could also pull a transmission line and start it up and see if fluid is being pumped. No fluid-no transmission pump.

If it were mine, I'd disconnect the torque converter, rotate and slide it in until it is engaged properly into the pump. Then start the engine while its disconnected from the flexplate and see if the noise is gone. I would want to eliminate the transmission as a problem and then move on to the next thing to eliminate.