Depends a lot on how you treat it. I was able to easily go 160k on my stock transmission, but I didn't drag race or abuse it daily, & I kept the fluid clean & cool. I knew the power was there & used it wisely. If I needed to tow 80mph, or spank-a-Ford, I would. Finally at 160k, I was slipping the lockup clutch in the TC, & had a Goerends Triple installed. While there, they opened up the transmission, & found just minimal & normal wear. It was brought up to date, & re-installed, the only real upgrade being the solid steel band strut lever or whatever it's called. I still don't deliberately abuse it, but the truck goes & tows like hell if I deem it necessary. (190k now)