833 trans, OD

The problem with running the small imput brg is the deflection at the imput/output coupling.
The 3/4 shift collar locks the shafts together creating strength in normal operation, - but with overdrive the collar doesn't lock the shafts, so the output shaft can spin faster.
The bigger input bearing helps take the deflection, where the weakness seems to be, and helps take load off the tiny rollers between imput/output shafts, now spinning all the time, as never before .
The case hardening usually fails on the output shaft .