I have a pitman arm puller that is larger than the others in my drawer, and at times, it even will not do the job. At That point, I remove the steering box and put it on the bench. I use a little head on the arm, and I mean a little, do not let it glow read, and attempt to pull it off. I have good success with that.
I know your not wanting to pull the box, but sometimes, on trucks, most of the time, you have to.