Finally can close this one out!!!
 

With my pending month long trip to Arizona, I figured I had better get the fill plug loose and get the gear oil changed. I had been trying once a month since getting the car on the road, but have been unable to free the plug. Today after work, I swung by Franz' shop and discussed my problem with him.

We put the old gal up on the rack and used his "special" shorty 14mm allen. The 560's need this shortened version to clear the leveling valve. I had been using my full sized model, and been unbolting the valve to gain clearance.

Well, long story short, it took both of us on the cheater pipe to break the plug loose. While we had it on the rack, we went ahead and drained the oil. I'm thinking now that the gear oil was the same stuff put in at the factory, years ago. It came out blacker and thicker than two day old coffee thats been sitting on the burner. YUK!

Went ahead and refilled with dino gear oil. I will let this slosh around for a few days, drain again and refill with the synthetic gear oil I purchased. I still can't believe how damn tight that plug was.

Definitely feel better about it now.

I probably put over 300lbs of torque on the plug to remove it on my '87 560SEL. Had a good 30 inches of leverage and most of my weight on the end. Shoulder hurts just thinking about how hard I had to pull. Had car up on stands and had also moved leveling valve for clearence. And this is on a car that had fairly regular maintenance in the past!

I use a short 1/2" drive by Herbrand # S-42. It works well with no clearance problems.

Mike - get the wobbler socket extension. You will wonder how you made it this long without one. Sears and Snap-On carries them and I'm sure there are other places that have them too.

What I did get for future gear oil changes on the 560 is one of those nifty Hazet wrenches. 14mm allen on one end, 13mm box on the other, embossed with a 117 part # and the Star. The allen is offset so there is a long end and a short end to it. It fits nicely between the diff and leveling valve.