- thanks everybody. I have ordered a 3/8 drive 22 mm socket - ---worth a try as a bit shorter. May well break. I will take about 10mm off length of my 1/2 drive socket this weekend and a big ring spanner may work. (Don't want to lift engine, or pull off the a/c and generator.) Now that I have the old arm more accessible it looks like main play is in the bushes rather than the ball joint ,;; no matter, have to get them off to replace the bushes I think, and I love this 928 Motorsport arms.