@Krazylegz1485 got the gist of this pretty much realtime but the tl;dr is I sheared off a rear diff cover bolt while installing a skid plate. Figure it's only a concern if I notice some major leaking but wanted to get the opinions of y'all.
The skidplate bolts to the actual diff? Weird. The ones I've worked with reach up to the diff mounting studs behind the subframe. Of course, then they collect debris and rot out the rear cover... I don't like that the skidplate is now attached to the one bolt there. If you think you're likely to sustain a hit that would require a skidplate, than there's a decent chance that second bolt will shear off, and now you have a big gear oil leak, likely far from help. For just street use, it should be fine, and even if it does start leaking, it'll be slow. I have run rear diffs missing multiple cover bolts, but I don't think it's ever been a lower one, and definitely not with a skid plate bolted on there like that. If it were me, I would weld a nut on there and give it another try. It's pretty easy, the weld won't stick to the aluminum cover, so you can fill the hole with weld until you can start into the nut. Otherwise, you're better off without the skidplate IMHO. The diff case can take a hit far bigger than the subrames can, that dinky little plate is just sending the impact force into the bolts, in a way they were never intended. And take the fill plug out in your garage, clean it up, and put it back in with anti-seize on it. And carry a 1/2" ratchet and a couple quarts of gear oil in squeeze bottles, so you can top off wherever you are. Maybe even remove the cover and reseal it with Great Stuff (will actually adhere to the surfaces, instead of the factory gasket that requires the clamping force of the bolts to seal).
Yeah, it's the mini unit from Primitive. They have a beefier one but the fit might have been questionable with the exhaust I have. I don't own a welder, but that's a good idea. Also good idea to hit the fill plug with antiseize. I had it out a few months back when I was trying to figure out a noise that turned out to be a wheel bearing. Classic. The main mounting points are just in front of the diff. The carrier I think it's called. In the 3rd photo you can see the two nuts I pulled. I think the rear bracket to the diff cover bolts is mostly to keep it aligned.
Yep, Primitive makes an Aluminum version, too. Bolts on to all 4 side bolts at the T-bar, and then up to the actual diff mount studs. Much stronger, actually ties the 2 subframes together. We did have one come into the dealership that had been on there for years, and the debris collected on the skid plate rotted through the rear cover and smoked the diff. I have seen a rally car without a diff plate hit hard enough to bend the stock subframe without damaging the diff. IMHO, a diff skid plate is useless without aftermarket tube subframe/t-bar/lateral links/trailing arms and gas tank skids.
