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Rear diff oil grey and muddy coloured

10094 Views 10 Replies 5 Participants Last post by  A10ThunderboltII
Two things I have.

Thing One: I changed my diff oil myself for the first time and the rear was grey coloured with the occasional strand of black in it. I'll put a picture up. The front was green and looked like new so I'm wondering if there's a leak in the back and it's filling with crud. My dealers closed or I'd call them but I'm wondering if anyone with a bad seal ever had the same looking fluid when they drained it.

Thing Two: I grabbed the wrong bottle off the bench and put 75w 90 in the gearbox instead of 140. Can I run at least a while or should I drain it and put the 140 in. That drain bolt is a BITCH.
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Did it look like this? That was my first rear diff oil change at 198 miles. Dealer said it was fine. Filled it back up with Amsoil 75-140.


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I'm trying to upload the photo but it keeps crashing my browser. I'll keep trying. Mines more milky and runny. I think water got in but I don't know how that would have happened.
Id say it looks like water and muck got into it
I agree but how I wonder.
Mraz036 pic is oil from a ticking time-bomb diff...the shiny stuff is the gears wearing out.

Fingolfin pic is water....lots of water. Mine was like that too....I think the new breather system (old ones had bellows) lets moisture in. It tee's in with the gearbox breather and runs to the airbox. I'm not sure how or why...but I change my rear diff oil 3 or 4 times a season and it always comes out milky. I just finished changing all the seals in the diff and installing a we will see if that helps.

Re thing two: should be fine. The 06 to 11 machines recommended 75/90 for both diffs and gear case.....changed to 75/140 for rear diff and gear case in later years.
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Thanks for the reply. You'd think if the seals were bad that it would leak OUT as well. I'll crawl under there tomorrow and see how that vent hooks up to it. Anyone have a suggestion for my other problem?
Thanks for the reply. You'd think if the seals were bad that it would leak OUT as well.
Not if its a breather tube ABOVE the rear end
That drain bolt is a BITCH.
One is 6mm, the larger one is 3/16" said my local Service Mgr.

3/16" ?? what happened to METRIC
oops, the LARGER one is 6mm, the smaller 3/16" = 4.762 mm
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