Had the truck towed to a diesel shop - they got the inspection cover off and found the flex plate OK and torque converter bolts were tight. The mechanic removed the oil filter, opened it and found no metal. He's absolutely certain the noise is coming from the torque converter or transmission. The mechanic was not impressed with the workmanship he saw on the transmission. Had the truck towed (it's that bad) to the transmission shop - I still have 2 years left on the transmission rebuild. If the transmission shop accepts the transmission/torque converter is faulty it will be 2-3 weeks for a replacement transmission. Even if it's only the torque converter they'll ship the whole unit out rather than replace the torque converter.