What input shaft did you have? The stock 4t65e can handle about 300hp. Not that I would want to push a stock trans that hard for very long.

Not sure what he relaced the stock one with but when he fixed it he cryogenically froze the rotating parts. it'* staying together now . it' supposed to be around 500 horse with the eelectric exhaust cutout opened. it will run 7 pounds with the exh. closed and 10 lbs. open

ZZP makes a 4340 input shaft, they claim 600hp, but I've heard a few bad things about it breaking with less then that. They also make a 300m which is good to 1000hp. I have not heard of any of the 300m shafts breaking. The input shaft is one of the most likely parts to break. There is also a hardened output shaft, but I have yet to hear of any breaking. It'* likely you had a bad input shaft. He has been putting down a lot of HP with his setup. Not sure on his HP, but he was running with a 2.8" pulley and intercooled, and I had him tuned for 22* of timing at WOT with no KR. He lost a rod bearing so decided to build a new turbo setup.

project update - picked up a motor with 38 k on it and it'* time to start putting humpty dumpty back together. any ideas on a limited slip or posi for these fwd trannys ?

There are LSD'* out there for them