Depending on the last time you pulled the arm off, you will likely need a press to get it out. I had one that I was disassembling for parts, that I couldn't break free with any amount of beating (fully soaked with penetrating oil) or pulling with a puller. I put it in a press and pushed the shaft out of the steering arm and it sounded like I needed to take cover when it let loose. It was not all that rusty either.