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  1. #1
    JK Enthusiast
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    Default black sludge comes out of differential?

    the fluid that came out of my rear differential looked a big like dark gray/black sludge. is it supposed to look like that? the front differential looked like oil when it drained, it had a bit of the sludge on the drain plug, but the fluid that came out was clear.

    just refill it with the new fluid? (mobil 1 gear oil)

    08 4x4, 16,000 miles, 1st change
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  2. #2
    Banned 09rubicon's Avatar
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    Default

    I would give it a serious look over before just refilling it. It should come out like dark oil, not as a gelatanous glob of sludge. Your front sounded about right, not your rear.
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  3. #3
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    Default

    Quote Originally Posted by 09rubicon View Post
    I would give it a serious look over before just refilling it. It should come out like dark oil, not as a gelatanous glob of sludge. Your front sounded about right, not your rear.
    i'll go pop the cover off, what would i be looking for?
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  4. #4
    Banned 09rubicon's Avatar
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    Default

    Broken ring or pinion gear teeth, spots on the teeth with gouges or serious wear marks.....basiclay anything that doesn't look normal (i know....what is normal). Seriously though, a little metal residue is normal from the break in and wear of the gears, as is black or seriously used/abused oil.....but alot of sludge is usually an indicator of something wrong.
    2009 JK Rubicon Jeep Green
    Rugged XHD "stuby" Bumper
    Superwinch EPI 9.0
    Gibson Dual Exit Exauhst
    PureJeep CAI
    KC Slimline 6" 130Watt
    TF 2.5" Coil Lift w/9550 shocks
    Spidertrax 1.5" spacers
    JKS Front/Rear Adj. Trackbars
    35/12.50R17 Cooper STT
    Cobra 75swt w/ 4' Firestick
    AEV Procal
    TF Front Lower Control Arms
    Crown SS Extended Brake Lines
    Great Lakes Off-Road Diff Covers


    My JK in ACTION


    www.northridge4x4.com

  5. #5
    JK Enthusiast
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    Default

    it looks like grease. it has a sparkle to it. i don't see any thing that looks abnormal... i'll take some pics before i spray it out
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  6. #6
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    Default

    is blue RTV ok to seal it back up with?
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  7. #7
    JK Freak JKMARINE's Avatar
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    Default

    What did you use to flush it out with? I used a couple cans of contact cleaner because of the high evaporation rate with no residue. I also used the red high temp RTV.
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  8. #8
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    Default

    sprayed brake cleaner in there. used a blue RTV. letting it set now.

    is it really bad if the cover slid when i put it on? i don't want a leak and i dont' want to do this for another 18,000 miles....
    Michelle
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  9. #9
    JK Freak JKMARINE's Avatar
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    Default

    As long as there is RTV around the whole cover, it should be fine. When you tighten up the bolts, it will squeeze out the bead of RTV. If you have no gaps in the RTV, it will be fine.
    JKMARINE
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  10. #10
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    Default

    it squeezed out, and i had a good sized bead, so hope it'll be alright. what a dirty job. even orange clean is having a hard time getting this crap off of me. and to think i was going to change the diff fluid on my grand cherokee. another time, lol
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  11. Default JK-Forum


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