mc-1 Upper housing reassembly question.

[ttownthomas]

I am re-sealing and going through my upper housings. The top cap outer bearing race and bearing rollers have corrosion and I assume I shouldn't leave them like that. (part of me thinks that based on their location they lack oil and probably have corrosion in alot of drives). If I replace the upper bearing I assume I need to check the preload on the upper driveshaft. Do I need to also re-shim the driven gear and drive gear?