My wiper started to hit the rain gutters at the end of it's travel and stick.The wiper arm was loose and I can manually push/pull it in and out a few inches. I pushed it back in, but after a couple wipes it works itself out again.

I took off the plastic cover on the wiper arm to see if the allen screw that holds the arm to the round stainless shaft had come loose (I was hoping this was the problem). I found that the allen screw was tight, and the shaft itself moves in and out.

I'm guessing this means that I have to open the wiper "gearbox" to find what has become detached, but thought I would see if this is a common problem. I've only had the car three weeks, and am still getting up to speed with w124 specific problems. I did a search, and found many wiper related threads, but nothing specific about this shaft moving.

Thanks in advance for any insights.

I think you are going to have to take out the assembly and open it up. I just had mine apart to grease it(91 300e) and I can't see how it would move as you describe without something worn out or coming apart

Thanks Rob, yeah I guess I'll have to open it up to see what's going on.

Are the gears available somewhere, or are they a dealer only item?

I read somewhere that Mercedes only sells the entire unit. I dont know if that's accurate. I would check after you know what you need. You may also find a local machine shop that can manufacture the bad part but that may be expensive. It takes as much time to set up to make one part as it does to make 50. I have bought used parts from a place called star mark recycling in California. They will ship to you. Good luck. Be careful when you remove the blade assembly. It is spring loaded you don't want to break the windshield