Guess I've been lucky as my pitman arms have always slid right off with just a little bit of pry bar help. Like Robyn said, remove the bolt. I spent a good amount of time trying to remove an arm while the bolt was still in place only to realize that the bolt goes through an indent on the pitman shaft. Once I discovered my stupidity, I pulled the bolt out and the arm practically fell off. Keep trying, you'll get it.