Drive shaft support skid plate bolt

I’ve been hearing a bunch of rattling at low speeds finally decided to figure out wtf is going on , upon inspection I hit the skid plate and noticed immediately a sound so I thought maybe just a rock but come to find out looks like someone may have stripped the bolt that holds this washer because it was just free in there rattling a bunch . Can someone identify what kind of bolt I need for this and am I safe to drive my truck .

 

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That is actually the Nut that holds the rear mount of the front diff in place, the hex portions is for an allen key to loosen it, there isn't a bolt that threads in from the bottom. On that rear mount of the front diff, you'll see the bushing above that nut, it has about 2" of thread sticking out that the nut threads on to. Yours looks like it's completely fine.
That washer doesn't go on that nut/thread assembly, but might possible go on the front 2 mounts of the diff, I would check and make sure both of those have a large washer on top and bottom of the bolt that runs through the frame. Or it also looks like the washer that goes on the Upper control arm bolt, if you had them replaced at some point whoever did it may have dropped that washer and it landed in the skid plate.