Originally Posted by the incubus

At this point the issue is somewhat (or becoming) widespread enough that it's impossible just one thing is causing the issue. Not across so many different people in different states, running different turn motors with different power bands, diff oils, etc..

The one thing I can say always sounded to me to be a bit too extreme is 100K diff oil because the resistance such thick oil poses might just be enough to place excessive enough strain on the spur, both under acceleration and deceleration/braking, and that might be fracturing a few teeth here and there until enough of them fracture that it lets go.

Think of how you can flex plastic back and forth until it begins to weaken and subsequently cracks or breaks. This is what I envision might be happening with the extremely thick diff oil. The DESC410 is considerably heavier than the 413 and generally a diff oil of 50K is enough. 100K oil in a 1/10 car seems too much.

I think the solution is an integrated slipper just like the DESC410 to provide some slip for the well being of the spur. these are tiny little teeth and perhaps too much is being asked of them.