[DeTomaso] My ZF is scaring me

[Campolieto Marc]

After a short ride yesterday I noticed a drip coming from the rear of my zf. I crawled under the car to see what the issue was and there is a small bump about the size of a pencil erasure with a crack in the middle of it. The drip is coming from there. I don't remember that being there before. There is nothing silver in the oil and the car shifts just fine. It goes into every gear. I put the car away immediately after I saw it. Any ideas? I am afraid to drive the car until I have some idea of what is going on. The ring gear is safety-wired and the crack is actually in the bottom of the rear case in one of those channels just behind the bolt. Any ideas?
Thanks,
Marc