I have posted before that it seems that an impact tool would be perfect for this. Using one of those cordless drills with the screwdriver settings would probably be ideal as they don't develop a lot of torque but that rap-rap-rap of the impact would probably free them up succesfully too.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz