[Fot] GT6 differential failure follow-up

[Scott Janzen]

Pulled my differential out and apart today - did not find what I expected.  
The input/pinion shaft is sheared off just forward of the pinion gear.  
The crown wheel has barely a mark on it, all teeth intact, no signs of damage.
The inner tapered bearing race on the pinion shaft is just mangled and there are roller bearings all over the place.  However, the outer races for both pinion bearings look fine - no sign of discoloration or overheating, significant damage, etc.
It did fail when I was decelerating in second gear at high RPMs down the steep downhill on the new course in Pittsburgh, so the engine promptly slowed down - still, amazingly, there is minimal sign of rotational damage to the driveshaft - just a couple of paint scrapes.  It was essentially unsecured at the rear, but perhaps the outer/forward pinion bearing kept it centered.
Both the shaft and the gear rubbed against each other so much there's no way to see any fracture marks.
One of the four bolts securing the spring to the top of the differential had cracked the housing, and it clearly leaked some oil there, but judging by the lack of oil on the underside of the car, I don't think this contributed to the failure.  I had just topped it up before the weekend, and there was no sign of oil under the car throughout the weekend.  Guess I'll be tapping the next diff for two more bolts, so there are six securing the spring next time.

Photos attached.



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