The most common cause of creaks up front is the sway bar end links and bushings, but that would not be easily confused with the upper ball joints since these are down at the bottom end of the suspension.

MB only sells the upper CA with the ball joint as an assembly. I have heard on other models that people have successfully been able to replace the ball joints on them but the whole arm is only $150-$200 or so therefore usually it is cost effective to just replace the entire arm assembly.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz