[rcweingart]

Obviously it is hard to diagnose without seeing/driving the car. Apparently there is no adverse functionality, no vibration that you feel, no drivability issues, more of an annoying sound that you want to locate and address. You've had the tranny disassembled twice without finding anything wrong and I presume the shifter as well. I suggest removing the tranny console top cover so that the tranny and all are exposed. Have someone in the car with a mechanics stethoscope, a rubber tube or some other other device to use to try to locate where the sound is coming from while the car is being driven and go from there.