Tire wear, what's causing this! ? ?

Don't just put the puller on the pitman arm and tighten down on it. Remove the nut, install the tool. Tighten down on it. I use an impact. Tighten it down good. Then remove the impact and socket and take a hammer and smack the SIDE of the pitman arm where it slides onto the sector shaft splined shaft. Tighten some more and repeat until the arm pops off the sector shaft. If you simply tighten the tool without smacking on the pitman arm, you will probably break the tool.