The following pictures are what was (unexpectedly) found when deciding to take care of an annoying leaking pinion seal. The differential in question is a #AF1229 (3.90, Happy New Year) from my '59 Apache.
It's like going under the knife for a hernia and the Doc telling you that you are all eaten up inside with cancer! A new seal, a new pumpkin cover gasket - oh my, look at this, it got worse in a hurry.
The previous owner had let it sit in a shed from about '08 to '15, but maybe this corrosion had taken place some years before - it's hard to say. As heavy as it is I sort of think so. Being in a shed, it was covered, etc. Maybe it was in a flood at some point in it's life. Since getting it running I've put about 3,500 miles on it, yeah, with it in this condition. Odo is showing 63,800.
Not being prepared for the extent of work and parts it would take to do it up right, we greased the bearing up, reassembled, refilled with 80-90 and buttoned it up. I've driven it 20 miles since and nothing's really changed. It still goes down the road, no new noises, not any quieter that I can tell.
Now, what's the thoughts on what direction to go? Run it like it is? (stock 235, no towing or any loads in the bed, flat terrain, highway speeds 30-40 miles at a crack). Or Don't drive it due to certain impending death
I'm inclined to keep driving it while I either a) source parts for a complete rebuild or b) swap out the whole diff for a similar year, (hopefully in better condition). Anybody want to sell a cast off 3.90 diff. cheap?