Try using a 4# hammer as a backup on one side of the arm at the splines a hit the opposite side with a 2# hammer. Just as you think you can't make another swing it will pop loose. Leave nut on loosely to protect threads.
Yep. I've used that method quite a few times. It makes the rust molecules let go and cover their ears.
Works really well with tapered tie-rod ends. Better than a pickle fork that screws up the rubber cover. A little pressure on the end of the shaft (with the nut on) and they pop loose.
