Brown Fluid From Rear Diff

beaufrusetta

beaufrusetta

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So...I finally got around to changing the rear diff fluid the other day (2004 Rubicon), and it came out brown (I'm fairly confident that the previous owner never replaced that fluid in 150k miles). The drain & fill plugs both had a tremendous amount of sediment/small bits of metal fragments on it. I ended up draining it completely and then filling it back up with fresh oil...but I'm fairly sure I need to take the cover off and thoroughly clean it up in there like I did with the front a while back.

Question...is the brown-ish nature of the fluid due to a seal leak (water/dirt)? I'm assuming the rear has seals similar to the front, that are to the left/right of the diff? Do those go bad, or is this maybe a seal that's gone bad where the driveshaft is connected?

Thanks y'all!
 
beaufrusetta said:
So...I finally got around to changing the rear diff fluid the other day (2004 Rubicon), and it came out brown (I'm fairly confident that the previous owner never replaced that fluid in 150k miles). The drain & fill plugs both had a tremendous amount of sediment/small bits of metal fragments on it. I ended up draining it completely and then filling it back up with fresh oil...but I'm fairly sure I need to take the cover off and thoroughly clean it up in there like I did with the front a while back.

Question...is the brown-ish nature of the fluid due to a seal leak (water/dirt)? I'm assuming the rear has seals similar to the front, that are to the left/right of the diff? Do those go bad, or is this maybe a seal that's gone bad where the driveshaft is connected?

Thanks y'all!
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Yeah that's typically caused from water intrusion. Was it milky & thick? That's usually what happens when water gets into the oil. Could have gotten in there from the diff cover, the breather, or the axle/pinion seals.

I'd knock off the diff cover & clean the diff out, have a look at the gears, etc... If you're not sure what you're looking at just post up a pic of what's going on.
 
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qslim said:
Yeah that's typically caused from water intrusion. Was it milky & thick? That's usually what happens when water gets into the oil. Could have gotten in there from the diff cover, the breather, or the axle/pinion seals.

I'd knock off the diff cover & clean the diff out, have a look at the gears, etc... If you're not sure what you're looking at just post up a pic of what's going on.
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Yep...super milky and thick. I’ll yank it in a few days and throw up some pics.
 
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TWiG01 said:
I would definitely take the cover off for a thorough cleaning and fluid change. Is the breather hose attached / in good condition?
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This...
If your breather is jammed up...that axle will find a way to breathe alright. Right at a seal.

That said leaks work two ways. If it's letting moisture in...it will let fluid out.
Do you gave gear oil remnant on your inner tire sidewall?

If not...maybe it's not leaking any more...who knows.
Make sure your breather is flowing free and then take cover off and fill with 75w140..

Go wheeling!!


We use only Mobil1 at the shop on everything. Gear Lube, engine oil, etc.
unless something calls for a product they don't make.

Good luck
 
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Check the vent line on the drivers side axle tube; ensure the hose is attached at the brake line splitter and in good condition.
Verify the other end of the axle tube vent line is attached to the gasoline filler hose and has the breather check valve installed.
 
Take cover off and hit it with brake cleaner. An entire bottle of it.

the brake cleaner will evaporate fairly quickly then reassemble cover and fill.
 
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TheBoogieman said:
ALWAYS remove the diff cover and clean inside when changing the fluid.
p.s. I swear by your avatar pic that you're a Vinny from NY. ;)
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I don't know how I missed this reply...my nickname that my Dad and his buddies all call me is "Vinnie"... hahahahahahaha

Oh and...since I've literally got everything else out of the Jeep right now, I'm going to do a fresh clean of both diffs...and check the breather tubes.
 
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beaufrusetta said:
Yep...super milky and thick. I’ll yank it in a few days and throw up some pics.
Click to expand...
I would put a little atf in its and drive it a bit before you drain it. ATF will help clean the milky oil out of it. Then hit it with some brake cleaner.
 
And but a new breather and hose on just for good measure. Do you drive in water deep enough to cover the axles? Axle seals could be shot letting water in....but you'd probably have oil leaking out onto the drums and the rear brakes would giving you trouble.
 
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