Hmmmm. Let me think on this a bit.
Possibly the bracket weld got wrenched and has pulled the case and cracked it. I have seen this happen elsewhere with welded brackets. That little bracket is not carrying a very big load at all, so maybe it go banged when the axel was out for some reason. Or someone was jacking the car by the differential and the jack slid back off.
Anyway, here's a possible solution.
Use some paint thinner to thoroughly clean the area. Use a good light and possibly a magnifying glass to verify that a crack exists.
If you indeed have a crack, the oil should start showing up again.
If so, drain the oil. Easy enough to do.
Then reclean the area. When thoroughly dry, apply some 3M weatherstrip adhesive to the crack area. This stuff is tough and stays put. Give it a day or two to dry. Then apply a second coat. And maybe wait again and apply a third.
Exterior application of a sealer like this won't stand up under much pressure from the inside. But there should be none. You can assure this by cleaning out the vent. It is located on top of the right side of the axe. It screws right off and probably is plugged, if it has never been cleaned. This will relieve any heat generated pressure in the axel, which will also help prevent lube from pushing through the seals.
The only pressure you will have is the inch or two of liquid column pressure from the crack being below the top of the fluid level. This is so minor that the 3M product should hold against it. I like using it in situations like this because when using it for weatherstipping, is gets everywhere you don't want it and doesn't come off (except with the 3M adhesive remover). It is tough and flows real well, too well sometimes.
Refill the axel. When I recently refilled mine, the leak in the front seal almost completely went away. The reason is, I think, because I was very careful to only put in as much oil as the book says. This is about 3/8 to 1/2 inch below the bottom of the hole. If the old grease monkey method of "fill it 'til it runs out" is used, the axel can become very over filled and create too much liquid column over the seal height, constantly forcing oil out the tired old seal as the car just sits in the garage. Check your book for the quantity, and use a pump to get it in, being careful to keep track how much is going in. Most oil bottles have some sort of quantity calibration on the side.
Best wishes on this. Let us know how it goes.
[ 03-11-2004: Message edited by: Brian N. ]</p>