Here's a question / new idea ...
Do the holes from the two Torx screws that hold the ball joint go all the way through the knuckle? More specifically, can you thread those screws in from the back side?
If you can do that, I'd make a little plate that can push the right-sized socket from the back side to press the ball joint out, tightening the screws in parallel to press the joint out. I'm generally concerned about collateral damage in cases like this, and go for the more finessed solution. If this is possible, and if it has a chance to work, the #1 goal while doing it is to keep things aligned (the socket, and both screws tightening) with the bore of the ball joint. If you are pressing and it is not aligned, you'll be making the problem harder for yourself.
If you can only get one screw in, but not two, maybe you can lever against that one. Pressing can be very different from hammering sometimes.
If neither are possible, I'd go the slide hammer route, mainly since that gives you the best chance of getting it off without damaging the knuckle. You'll want to eliminate as much compliance as possible in the area to make this work, and align the slide hammer with the bore hole.
EDIT - another idea, a little more things to do, but almost (
) guaranteed to work:
- Get some longer screws that will fit into the existing two holes.
- Get/fabricate/hack together a plate with two holes in it to fit those two longer screws (through holes), and a third hole to fit the ball joint stud (through hole).
- Use the two long screws along with a couple of nuts to hold the plate a couple of inches away from the ball joint (as close as possible, but far enough for the following to work ...). Adjust as best as you can to make the plate perpendicular to the ball joint bore hole
- Use the original ball joint nut (castle nut?) on the ball joint stud (which is protruding through its hole in the plate) to gradually tighten.
- Hopefully the two screws keep things aligned, and the ball joint nut will provide a steady, aligned, *pulling* force (which in cases like this is always better than a pushing force, since it is self-aligning vs. self-binding). If you are unable to stop the ball joint stud from spinning while torquing it, then just tighten it as well as you can with the other screws+nuts loose, and then apply the separating force by carefully alternating between the two nuts.
- As I usually do with separating things like this, I'd get things loaded up with a good reasonable amount of force, then tap with a hammer to hopefully provide something to trigger the actual separation.