741 pinion nut torque too tight- did i damage it

It has been years since I worked on a 741, but I think the pinion bearing preload is adjusted with shims. A shim could have stuck to the old yoke, and when you installed the new yoke, you tightened the preload too much. It has happened to me on gear setup before. I don't think your electric impact overtightened the pinion nut.