the last W124 with the 3.2 litre M104 christened as the E320 did not have replaceable ball joints. you have to buy the entire arm.

The last gasser W124 that could take them was the 300E 2.8 of 1993, all diesels including the 1995 E300D had replaceable joints.

To make sure, turn the wheel and look at the joint/arm boss - if you see that it has 2 projections (shoulders) and has a rectangular shape where the joint is - then its replaceable, If you see a triangle section (like a pizza slice shape) then the joint is cast into the arm boss and is not replaceable.

To test it raise the car on jackstands and take a strong 2x4 and try to move the wheel a bit in and out from the bottom, if you can move it, the joint is bad and requires immediate replacement. The W124/201 ball joints are under pulling stress and can cause very dangerous incidents if the joint lets go.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)