I have a '92 F150 with the M5OD transmission that is making a metal on metal sliding sound. The sound is loudest while shifting into 2nd gear but can be heard faintly while driving in 1st and 2nd. Im thinkin mainshaft bearings? How long might this last before catastrophic failure? Does a rebuild of this transmission require alot of precise measurement or shop press work?

Any help is greatly appreciated
tinker89