I believe I found the source of the metal. The front planetary seems to have been rubbing up against the back of the rear clutch retainer/input shaft. My transmission Knowledge is very limited. Could this be caused by using the wrong selective snap ring(too much clearance) on the planetary set? Reading through the 727 transmission handbook I also see that 1978 and up transmissions had a thrust washer and steel race. Mine only has the single #3 thrust washer and I’m wondering if that isn’t providing enough clearance.