
No way is a regular impact going to get it tight enough in my experience. If you can loosen the nut with a breaker bar then it is much too loose. You need it tight enough so that you need a long cheater bar to break it loose.
Just to be clear, you need the thing that looks exactly like this:

It slips OVER the nut itself.
Just to be clear, you need the thing that looks exactly like this:

It slips OVER the nut itself.