Machines in thus class may seem to us to cost dearly but when it comes to the overall scheme of things, they do not have the precision ground gears found in high end machinery. Your front axle does not have a filtration system so it has the next best thing - a magnet to remove the wear particles that the gears in this system will continually generate. Excessive is when you find chunks instead of "iron filings". Systems with filters should do better but I have seen numerous posts here with surprising amounts of wear particles on magnets yet seldom hear of any major catastrophic failure. I keep a picture record at each service interval and once a year have oil samples analyzed, probably overkill but that was part of my pre-retirement life. If you have pictures I am sure you will get dozens of opinions.
