How do I get it out

 

Depends on just how you managed to break it.

Is it broke off below the surface ??

enough left to weld a nut to ??

Different methods depending on just how you broke it.

 

Pictures would help. And which bolt? Because the diff cover is welded on. Year make and model will help.

But you could always drill it out, then re tap if needed to or use an easy out. Heat will always be your friend. Once you get the diff out can is there enough room to get vice grips on it?

Welcome to the forum. But help us help you. The more details you can provide the better. Remember, we cant see what your looking at.

 

Pull the entire third member out, apply vice grips land turn to the left.
it is a stud