Due to senior moment, I can't recall if it has been 10 years or 8 that I've been working on these, but I'm sure I've never seen a small bevel gear fail like this before. At first. i thought maybe the woodruff key failed and let it get out of sync with the large gear, but key and inside of gear look OK. All teeth of big gear look good too. I see in the pic what looks like a crack in gear, but it is just a bit of grease - gear is solid. Could it have been a bad heat-treat????