Well, I thought this would be a question about the differential pinion seal. But that's not the problem.

Recently, on the 242, I had noticed oil on the bottom of the diff. I got under the car today to inspect it. Pinion area was dry as a bone. It turns out that three of the screws for the cover plate were a little loose. Two of them weren't bad but they needed a bit of a twist. One of them I could turn with my fingers. So I got them squared away and also checked the drain plug because that's where most of the oil was and it didn't seem to have migrated, i.e. there was some dry surface between two oily areas.

But the drain plug seemed plenty tight. So I wonder what is going on. Is there a crush ring for that plug? I don't see one in any of my exploded diagrams.

While I was under there I checked the vent tube. It was clear. And I also removed the fill plug. The oil level is adequate.

But this has me wanting to drain the diff, pull the cover, put on a new gasket and make sure the plug is sealed tight.
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'80 DL 2 door, '89 DL Wagon