Silver Colored Read Diff Oil

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Jun 6, 2017
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Hello, I'm new here and hopefully some of you experts can help me. I have read several threads about "silver" or "gray" colored rear differential oil in the drain pan at the first rear diff oil change, usually at relative low hours of use. Some say it is metal contaminate. I've read it described "like silver paint". I first read this in the Can Am ATV Forum, and my google search discovered similar stories in Polaris RZR forum, motorcycle forums, Jeep forums and even pickup forums. The internet search refered me to this site. Not everyone has this observation. Most folks assume the rear differential is doomed to failure. I spent more than half of my career in hydraulics. I've analyzed contaminated oil, both particulate and moisture. I've worked with red ATF, mostly clear Mobil DTE products, various colors of grease, but I have never heard of a "silver" colored gear oil. Some wonder it it could be a mixture of white lithium grease used in the assembly process in the gear oil. Others wonder if it might be anti-sieze used in the assembly process. I wonder if it is an additive used to assist in break in or keeping the gear mesh a bit quieter. Anyone have any ideas? dbj216
 
Joined
Jul 2, 2007
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Chicago, IL
Our Subaru's rear diff came out black-gray at about 9000 miles on the unit. I think some kind of assembly paste was used. Someone here observed the same on their low-mileage Subaru and had it analyzed, but no metals were high. Something organic based?
 

dbj216

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Jun 6, 2017
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CO
If I find "silver" oil in my Can Am ATV rear drive I will have it analyzed. I just hopeful someone will know what this might be.
 
Joined
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The slurry you find stuck to a magnetic diff drain bolt is silvery, so it stands to reason that we're talking about ferrous wear material. I installed a junkyard automatic transmission once in one of my cars. Unbeknownst to me, it was a turd. When I first drained the fluid, a ton of water came out of it. I proceeded with the installation as it was too late at that point to do anything else. Long story short, it kept clogging up the trans filter and stopped moving the car. So I did a series of back to back oil and filter changes, dropping the pan each time. The bottom of the transmission pan was coated in silver slurry too. I did have a couple magnets stuck on the pan in different spots so that helped attract some of the fine particles to that area. After about four of these changes, the trans stopped slipping and drove normally. I drove it until it failed completely, which was about two years and 15,000 miles later. After that I reinstalled the original transmission which I thought was failing in the first place. That transmission is still going strong five years later. Goes to show.
 

dbj216

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The ATV rear drive isn't a differential so to speak. It is a ring and pinion gear set (straight tooth I might add) driving a single output shaft. There are three ball bearings and three seals. There are some "shims" to set backlash and preload. It is a most simple mechanical component all wrapped in an aluminum housing. There is no differential planetary gear set in this drive. See exploded view below. There is a quart of synthetic 75-140 gear oil in it from the factory. I don't know the maker of this oil. It doesn't make sense to me a guy could get a large amount of metallic contamination in 25 hours of use. Maybe the gear set is made out of aluminum! And the fact that other forums talk about silver or gray colored rear differential oil leads me to think it is some type of additive. dbj216
 
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Nov 8, 2003
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Cape Cod, MA
When I changed the gear lube in my 2000 Grand Marquis with 127,000 miles, it came out like some sort of metallic silver paint had been mixed in. I was concerned that something was failing/failed already but the diff makes no unusual noise and has been fine since the fluid change over 3 years ago. For the record I put in M1 75W-90.
 
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