Sausage,
I know you mentioned the wailing just prior to failure, but did you notice any other unusual sound or vibration coming out of the drivetrain leading up to the failure? If so, give us a description of that.

 

For the last 5-6 months I've had a whirring noise from the trans area - I wrote it off as an aging bearing because it didn't get worse over time and a gear oil change yielded no metal fragments or particles. I autocrossed it and drove it every day with no problems until this.

I haven't torn apart the trans yet, but I believe I have a failed spider gear I'm the diff. I don't know if the whirring noise I had been hearing was from the trans or the coupler, but the wailing I heard upon ultimate failure was definitely sheared splines on the TT/coupler.