2 axle stubs broken in 1 weekend
 

I had previously never broken an axle stub but heard of them failing. This past weekend at Hallett the left stub snapped in half at the figure 8 on Friday, fortunately I was carrying a spare thanks to the advice of jgrewe. Sunday the right stub snapped in half in lap 2 of the race. It's an EP car with 13b NA street port, Jerico and clutch type NA LSD. Both times it happened after a 3-2 downshift at different spots on the track. This was a new to me diff with a custom R&P that I had just had rebuilt so the stubs had an unknown history.

Looking for some opinions to prevent this from happening again. Was thinking new stubs from Mazda are better than used street car ones and maybe some type of heat treating? Quick search didn't show any aftermarket stuff for the NA diff.

This is a definite spare to carry and easy to change out at the track. Be sure you carry a new axle seal as the old one will be destroyed.

I suspect something is up with the diff...creating extraordinary shock loading in an asymmetrical manner.

Not been to Hallett, are the curbs pretty significant? Was this braking in a straight line or under trail?

Where did they break?

is it possible the cir-clips were failing/ not seated right after the rebuild and the stub axle popped out then broke?

I only ask because after replacing an axle seal that happened to me and the stub shaft itself twisted and wouldn't go back in the diff:

https://lh5.googleusercontent.com/-G...UNSET%255D.jpg

I always hit curbing but both times it was straight line braking, long straights and a 3-2 downshift on different corners. 3rd is over 100mph.

The diff was a 4.88 out of an ITS car I bought off someone and had sent to a very respected well known guy to go through and rebuild (spent $750 on that alone) so the diff was in good shape. The axle stubs were the ones that came with the diff and of course were subject to much higher stress and power in my EP car and my drivetrain is also solid mounted. I am thinking the stubs may have had stress cracks from prior?

This is the left side, I haven't pulled the right one yet but it's in the same general area. The stubs were definitely seated completely as I installed the diff myself.