I had this with the f30. It uses a torx t40 counter hold. The thing was so seized it snapped my snap-on t40 socket. Went to Lowe's picked up two Craftsman t40s and it snapped both of them too. Not enough room to get the impact in. I tried some u-joint extension stuff couldn't get it.

Since I was replacing the arm anyway, I ended up just using the multi oscillating tool with the metal cut tool and plunge cut the stud below the nut. Easy enough. That oscillating tool comes in handy rather often.

Ball joints of the worst part of the car to work on. I had quite a fight with the one here on the e53 and had to use the torch. I've not found a good BMW ball joint popping tool. The off-the-shelf ones are too small. I've broken two of them.

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'05 E53 3.0 6mt
'17 F30 340ix 6mt
'96 E36 328is, in progress