Cant remember if theres 2 or 3 screws. I believe 3. Worst part is I just tightend one the other day and it already escapes me. This is a fairly common problem on high mileage SD's. If your getting one to snug up but it works its way back loose put lock tight on it. As for the other one, try to get a mirror up there to see how bad its stripped. Asess the situation to see if you can tap it and run a bigger bolt in or if lock tight will work on that too. They are driveable with one tight screw in but it will come loose often from the pressure of moving it. Make sure that the base is lined up to the screw hole.