Like input shaft change every 12 months. I forgot, and this made month 13 and it popped last Wednesday at Ohio Valley Dragway. I got the it pulled out last night. The shaft busted real nice and clean. It has lines radiating out from a spot 1/3rd from the center. It should be back together for the Black Mountain Diesel dyno day/sled pull next weekend. And defiantly at the Saint Louis race.