When is a ML320 Ball Joint not a Ball joint ?
 

I have a 1999 ML320.
Last week replaced the drive shaft bearing.

When looking at things, discovered the ball joint was worn out wil 1/4" of play.
That explains my handling problem and tire wear. The stabilizer bar looked worn too.

So I ordered a new Rear ML320 Ball joint and Special socket.

They arrived ,,,then apon further inspection what I bought was some upper
ball joint. Maybe what I need is a Control Arm Ball Joint. But it appears there is no such thing. Am I forced to buy and replace the whole Left Rear Control Arm as ther ball joint in it is non replacable ?
Thank you.
Steve

What was the part number?