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.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.