Hey everyone, my first post in here. Hoping to find some help as I'm all out of ideas. I am replacing the front lower control arms on my 07 S550 (not an airmatic), also called the thrust arm. I was able to get the passenger side off and replaced. However, the driver side is stuck beyond belief. The pickle fork I have won't work since the teeth are butting into the knuckle before getting far enough in to pop the ball joint out. I have a ball joint separator but I can't seem to get it on far enough that the top piece covers over the top of the ball joint stud. It covers it, but not enough. When I tighten down on it, the ball joint separator eventually flys off from all the pressure. I have gotten it to the point where it tights down so hard that it deforms the top of the ball joint stud. I have banged on the control arm with a hammer. I have placed a jack under the knuckle to help to hold it steady against the banging. I have sprayed WD-40 on it. I have tried everything. I even paid a mechanic off of craigslist to come over and try. He brought an air-hammer with an attachment that fit right in the torx hole at the top of the ball joint stud. After about an hour and a half the mechanic sighed and threw in the towel. Said he had never seen a ball joint stuck so badly. Is there something I am missing here? I can't wrap my head about this. When I got the passenger side off, I seemed to find a spot where I was able to get the ball joint separator pushed in far enough that the top part fit adequately over the ball joint stud. But no matter which angle I try on the drivers side, I'm not able to get it on that far.

Any suggestions are very much appreciated. I really need to get this job finished. Thanks in advance.

you can see how the top of the separator doesn't fully cover the top of the ball joint stud

 

Try modifying the lower stationary legs of your separator to get deeper under the joint. You will have to apply heat to the knuckle to get it to expand while applying force with the separator. I have had joints that eventually break free using heat.
Try using a small torch such as this one from harbor freight which has a nice sharp flame. I also use a small hammer to tap on the top of the movable arm of the separator while tightening. I believe heat is the answer.


Also, you may need to shorten the joint stud protrusion so that your movable separator arm is applying more straight down force on the joint. Right now, your force is pushing and bending the stud and is being deflected. If you can get a hack saw in there or grinder to shorten it that may help as well. I see from the pictures that you are at the top hole in your separator. It would have been nice to have another 3/8" of height!

Good luck,

Bob

 

I know this is an old post but I have to give a thanks to Bob. I was in the middle of control arm replacement and couldn’t get the ball joints to budge. Searched and found this thread, followed your advice to grind down the studs and apply heat. Worked perfectly!