I had the same problem with my 99 S/W your wiper blade arm is striped you either have to replace the arm with a new one or do what I did I applied a thick coat of epoxy glue into the inside diameter of the mounting hole and let it cure.Chased the hole with an undersize drill bit, Then I mounted it back onto the splined shaft that it mounts to and then tighten up your mounting bolt,it has been working four months.