Rear transaxle fluid smells awful – Normal?
 

I changed the rear transaxle fluid in my 1985 500SL Euro model. I never smelled such a foul odor. I cleaned up the spills but my garage still stinks. What is the story on the stinky fluid? What is it that makes it smell so badly?

Steve

I noticed that even the new fluid (Mobile 1 75w90) does not smell so good.

Bo

I can't tell you why, but I can tell you its normal. Probably something about the heavier components of crude oil being left in to thicken up the viscosity.

I wonder what crude oil smells like? I don't know but have a suspicion that I'm better off not living near a refinary.

Incidently, I just changed differential oil last weekend, and went with the Mobil 1 75W90 synthetic. It's not something you change that often so the expense (about double) is not that relevant. I did notice on the label that it has a "carrier oil" which I presume came from dinosaurs - so it does have a bit of that heavy oil smell.

So I do recommend the Mobil 1 synthetic for the differential. Seemed to run quieter and smoother afterwards.

Ken
'82 300D

The smell is normal. In regards to the synthetic oil - the Mobil Lubrication Engineer explained to me that synthetic oil is NOT absolutely 100% synthetic. During the crude distallation process they capture some of the lighter gas/liquid from the very top of the column which is used in a chemical process to manufacture the synthetic stuff. The stuff coming off at the top of the column is the absolute BEST stuff from the crude. The lower quality stuff comes off at a lower section of the column - diesel fuel is above #6 fuel oil and gasoline is above both of these, etc. #6 or "bunker C" is probably the least refined stuff.

don't ever spill any on your carpet or you will live with that odor for a long time......
William Rogers......

Yessir, that smell stays around for years.

I had been out of the oil patch for about three years when I came across an old pair of coveralls I wore regularly. They had been duely washed before being packed away. Three years later, not only the coveralls but everything in the box reeked of heavy oil. Fortunately there wasn't anything I really needed to keep in there, so I tossed the lot.

Try a mop with pinesol and hot water That is the only thing I've found that works. Even my pressure washer only knocks down the smell.

Thanks for the info!
 

I thought it was something like bacteria in the fluid. I didn’t think the new stuff smelled badly but I may have been desensitized by the smell of the old fluid.

I will mop with Pine Sol and see if any rag is lying around with the fluid so I can toss it. I will be more careful next time not to spill. The garage still stinks.

Steve
’85 500SL Euro

I asked a machinest/motor head at my work about that. He said its cause the oil is rancid. It makes some sense, motor oil only lives a couple of months, gear oil lives several years.