Dang Jim! That’s crazy.
I know mine has hardened input and output shaft and steel input hub. But for what he’s doing I wonder if it will be ok running 10s.
I know Rick Allison gives a general recommendation of 800hp and above 3,000lbs, he recommends the aftermarket shafts.
A friend of mine was doing the burnout contest at carlisle one year and broke the output shaft at the end of the front planet splines. Car was stationary , 383 - 2bbl in a 69 Satellite wagon. What happened was the spiders in his single track 3.23 gear rear end seized on it's shaft shaft and in the split second it took for the spiders to break into pieces it shocked the driveline enough to break the output shaft. He was lucky because the rear sprag in the trans was also rolled, I don't know when that happened though as he didn't really beat on the car outside of that one burnout contest.
