2001 Lincoln LS Rear Upper Control arm Removal

I'm in the process of changing the wheel bearing and took the brakes, disconnected the sway bar, and other large bolt but can't get the upper control arm disconnected because once the nut gets to a certain point, the ball joint starts spinning with it. Tried holding the bolt at the bottom with vice grips and it still turns. Any suggestions or anything I'm doing wrong? I'm thinking I might have to take off the whole A arm if I can't get this nut off.

The nut for the upper ball joint should have a hex end on the shaft, correct? Once you get to the point where the ball joint shaft starts spinning, use a box end on the ball joint nut and a (much smaller) box wrench to hold the hex tip and keep the shaft from spinning. The good news in since the ball joint shaft is spinning, you shouldn't have any difficulty getting the knuckle free from the joint once you get the nut off.

-Rod