While replacing a rear end right axle seal, this came out after I pulled the axle shaft out. when I was trying to get the slide hammer lined up, I pulled it out to adjust the hook and this was pulled out. Any ideas??

Thanks

 

That looks to be the spring from the axle seal; it creates tension for the seal to stay tight against the axle shaft. The new seal should have the same thing in it.

 

OK thanks. Just wanted to make sure it didn't go back in.\

I bought the seal from Ford, so should be there.