Spray the inside with PB Blaster. Let it loosen up the rust and wipe it off. Do it several times then pour some oil in on the bearings. See if it rotates smoothly. If so run it. If not get a bearing kit from dr diff and replace the bearing.
Oh it rotates super smooth right now. It was a little stiff on like 3 splines of the gears where a little surface rust was. Those 6 faces of gears are the only portion of the rotating assembly that has a little surface rust on it.
