I have a 627E, 6GB00686 serial that when I gave it a 500hr service the front transmission filter was full of yellow metal, including the oil. I dropped the trans oil, which looked pretty clean, and check the screens and magnets. Some debris on the screens and magnets but majority of the debris was in the filter I believe the oil path is from the differential portion of the transmission housing, through the screens, pump then filter, so I pulled the charge and scavenge pump to strip and assess. No abnormal wear found. I made the call and pulled the transmission. On inspection of the transmission parts, no abnormal wear is found. Another experienced mechanic suggested checking the retarder for the source of material. Has anyone come across very fine bronze or brass looking particles in the filter before?
When I worked on the mountain (ski resort) we switched to Schaefer lube for our snowcats and their was additives in it that at the time ate brass and bronze idk it wiped out quite a few pumps before we caught on
I haven't worked on any Cat pans in the past but have had a couple of torque converters and retarders apart in haul trucks. As I recall there are brass bushings in the retarder wheels. The retarder is just a big paddle wheel with a nozzle aims at it. The other possibility is that it is all prior damage that wasn't cleaned out. Were there any complaints before you did the service work?
Yellow metal is most likely from either transmission planetary thrust washers (depending on the age of the transmission, later ones were plastic), or differential gear bearings / thrust washers.
I thought that as well but the OP stated they pulled the transmission down and saw no unusual wear.
What does the bushing look like where the drive shaft runs through the differential?