This past weekend I had to change my passenger side axle u-joint and when I removed my axle this thing popped out with the axle. When I saw I thought it was an outer seal and put it back where it was. Now it is not seated and is rattling between the axle shaft and the axle tube. After doing some research online I cannot find what this is. Anyone have any idea what it is and can I remove it?

 

That’s an aftermarket seal. It’s not an oil seal, just a dust seal. They’re not super useful, just keeps dust out of the axle tube. You can either remove it or secure it back into place.

 

I'd remove it. They might keep some dust out but they aren't perfect so when water and crap gets by it's all just trapped that in the tube. You basically swap one issue for another.