A new gearbox failure mode

The dragcar gearbox had an interesting failure on the last outing.  Manifested as partially blocked third gear.    Initially what I thought was the snap-ring that holds 3rd turned out to be the 3/4 Hub on the input shaft.  The corners of it have fractured off.   The bummer here is that even the magical Quaife kit does not address this.    Not much initial damage here but the bits ended up in all the wrong places.  :(

Has anyone out there experienced a failure like this? Possibly a fatigue failure from some harmonic (9k rpm and solid clutch disk) or a mechanical overload.   I figured it would have killed the 1/2 since the loads there are much higher on slicks. This box did shear a handful of axles.    Next step is the material science lab and look deeper into the material properties on the variations over the years to hopefully find a tougher one.

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1 Comment  »

  1. John Williamd says:

    Yes, had same issue here, third/fourth gear hub broke into pieces after some axle stub axles broke and some weird things on the dyno. Could not shift into third or fourth, found the hub broken, similar to your box.
    John

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