Funky Chocolate brown gear oil

[GreeCguy]

Sorry that I posted this elsewhere, but I'm still a newbie and getting used to all the cool areas o this site.
Could someone tell me what's happening here. Yesterday, I drained the rear-end on my father's old Case D tractor. The tractor was made circa 1950. I think the gear oil in the rear end comes from 1950. It is very, very, very think and heavy AND looks like milk chocolate. It doesn't smell bad like most rear end/manuel tranny fluid does. But it is in no way the amber/clear color. Does anyone have any idea as to what happened to this fluid over the years? I'm guessing when it was new, it must have been a 90 weight gear oil. Now, it has the consistency of warm tar. Any ideas?
Oh, by the way, if anyone needs any antique gear oil, I have 15 gallons

 

[Stinky Peterson]

Hi GreeC

Well if it is that old it is probably severely oxidized and contaminated with water. You can test for water by putting a drop of oil on a hot plate heated to about 350 degrees. If water is present it will boil whereas the oil will not. You probably will want to flush it out good by putting in some 10wt or other light oil and running it around to mix things up. Don't put any load on, just drive it around the drain it out. You might have to do this a couple of times especially if water is present.

Good luck