20 year old gear oil from NOS 8.8 diff

Joined
Aug 6, 2022
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I purchased a NOS (new old stock) Ford Cobra 8.8 diff from a local guy that bought it from an auction where a Ford dealership had recently closed. Had a chance to see it in person before buying but he didn't want me to open up the cover since it had oil in it. Everything else looked original including a Motorcraft tag, no sign of wear, factory plugs, etc. The metal tag indicates it was built in 1997.

Got it home and drained it to find a very odd looking white/tan fluid and thick white substance collecting on the bottom of the diff. The amount of oil seemed to be what a typical "factory fill" would be and it had the odor of gear oil though a little funky. Until I can show it to a local transmission expert I trust to see what he thinks, I figured I'd post here for input. I currently have this same type of diff with the Ford "Trak Lok" in a different gear ratio, and I know you need to add a small bottle (8 ounces?) of friction modifier. Could that be what has caused this oil to congeal, turn white and smell funky? Does gear oil do this if unused for 20 years?

I'm thinking of pulling out the ring gear to clean it all out, and then soak the bearings in mineral spirits and re-oil them before reinstalling. Going to put new rubber axle seals in it as well due to age.

Thanks for any input

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Oil that looks like that you would think water was the issue but there is no rust or sludge that formed on an air to liquid interface but even then the only way to get it milky is to have run it with water in the oil. Possibly the additives dropped out of suspensions?
 
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I dont see any rust I would hesitate to put anything not lubricating in there.
just wipe it out good. maybe do a short gear oil change

ie 3000miles with supertech. then change again.
 
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I would put new gear oil in it, run a few thousand then change it. You will be good to go
 
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I agree with the others - wipe it clean and run a short OCI to clean it out. Supertech would be a great option in this case then refill with whatever "good" brand of synthetic gear lube you like.
 

pj-mcg

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I agree with the others - wipe it clean and run a short OCI to clean it out. Supertech would be a great option in this case then refill with whatever "good" brand of synthetic gear lube you like.

When you say Supertech, do you mean the cleaner? I've never used it but I see it as bottles of fuel injector cleaner, general purpose cleaner (sounds like carb or brake clean). You're talking about just to clean the goo out? Or is it something else you run with the gear oil?

Thanks for the suggestions. No condensation or any surface rust in the case, so probably not water-related. Not sure what they use for gear marking compound at the factory but that could be it based on the thickness and appearance.
 
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When you say Supertech, do you mean the cleaner? I've never used it but I see it as bottles of fuel injector cleaner, general purpose cleaner (sounds like carb or brake clean). You're talking about just to clean the goo out? Or is it something else you run with the gear oil?

Thanks for the suggestions. No condensation or any surface rust in the case, so probably not water-related. Not sure what they use for gear marking compound at the factory but that could be it based on the thickness and appearance.
I was referring to the supertech gear oil as a 1st run.
 
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