Differential oil

This morning I drained the oil from the diff; I was surprised to find really clean oil! I found a magnetic drain plug that had just a slight gray type residue...no doubt minuscule metal shavings attracted by the magnet...cleaned it and reinstalled it. Refilling it with Redline 75W90 NS. 

My differential feels really good...tight without any play. Feels direct and connected....I think I'm just going to clean it up, paint it and reisntall.  Certainly it's coming down while I restore the body. There is a leak and I'm not sure if it's coming from the drain plug or front seal...there must be a seal....right? Need to research. I'm wondering if I can service it without a full blowned brake down. 

Topped off with new fluid.