On my 2005 4.4, both ball joints (never replaced before) came out easily (without using any special tools) after thoroughly spraying liquid wrench all around the ball joints a day earlier and a couple of hours before attempting to remove them. The driver side popped off just by tugging side to side the still connected arm. The passenger side required two light blows on a screw drive placed on top of the ball joint and it popped off right away. Leave the arm still connected to provide leverage.

As a couple of others have pointed out, I would say the critical factor is to apply liquid wrench well in advance of the project. The ball joints were rusted on and thus I think it would have been extremely difficult to remove them without thorough lubrication. You have to give ample time for the liquid wrench to seep through the joint. I was surprised how easy they were to remove.

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'05 E53 X5 4.4i, '97 E39 528, '07 E92 335i, '16 F86 X6M.