Thats the 2nd shaft I've ever actualy seen that broke. The other was years ago in Dan Dye's blown alcohol modified street Cuda. Doug
Monte Smith broke one years ago, running a load of nitrous and over 1,000 hp. That kind of a combo would provide the shock and or torque load strong enough to kill stock shafts. So depending on your combo, like mine, under 1,000 hp should live a while.