Went through a phase of breaking these a few years ago. checked driveshaft at the shop that made it...Ok, Changed trans mount from stock to urethane piece, and checked length and pinion angle... broke one. Added an engine limiter and snub bars to the cage... broke one. Had the drive shaft checked for balance and out of round at another shop... said it was "ok", broke another one. Ordered a brand new aluminum shaft from Inland Empire Driveline... never broke a tail again.

It was funny... the change that I made was putting my newly ported heads on and went from running high tens, to low tens/high nines.