First thing I would try would be with the engine cold, take off the serpentine belt and then start the engine. If you still get the noise, then it is nothing that is belt driven (alternator, AC, water pump, belt tensioner, etc) If you don't get the noise, then its something belt driven, which would be preferable to an engine or tranny making that awful noise
Don't run it without the belt for very long, don't want it to get hot with no water pump
only other thing I can think of is use a piece of hose as a stethoscope to see if you can narrow down the noise source location
