Yeah good point, I checked the bearing on the donor gear and it was in fine condition. You're right, there was probably moisture in there, and it looks like the 4wd wasn't used for a long time, so the front output gear sat in one spot, getting rusted.
I'm going to pull the case apart again, get new gaskets and install the 3 matched gears from the donor case. I don't like having doubts when running something.
