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308 differential seal replacement

Discussion in 'Technical Q&A' started by chairpilot, Sep 5, 2011.

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  1. chairpilot

    chairpilot Formula 3

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    #1 chairpilot, Sep 5, 2011
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    My 308 is starting to throw oil out from the passenger side seal "B". "A" is showing early signs as well. After pulling aside the 1/2 shafts, etc. - can I replace these two seals without pulling the engine, taking the cases apart or other extreme measures? From the diagram, it appears I could do "A" by removing plate #54. But, I'm not sure what the deal is with the "B" side.
    I do not know what the part number for the upper half of the diff case is but maybe that can be lifted off to do the two seals?

    Thanks for any insight on this.

    Bob R.
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  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Sep 5, 2011
    Don't remove plate #54 -- just pull the seals out with a seal puller or the sheet metal screw method. No serious disassembly required.
     
  3. chairpilot

    chairpilot Formula 3

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    #3 chairpilot, Sep 5, 2011
    Thanks Steve. Do you know a good source for the seals? So far I found one for $37.50 each. I believe the size is a 45mmx62mmx10mm which hopefully is generic so I do not have to buy one in the horsey box!!

    Bob
     
  4. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #4 Steve Magnusson, Sep 5, 2011
    No, I've got no better price from a US source for that seal. SuperformanceUK's price is much better, but the shipping cost/hassle might make it a wash.
     
  5. chairpilot

    chairpilot Formula 3

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    #5 chairpilot, Sep 5, 2011
    SuperUK, yes - agreed. A Google search of the seal in that size turned up multiple hits including this one:

    http://www.colonialseal.com/33352.html

    It seems there are many variations of this size seal in terms of the cross sectional profiles. I may need to first remove the existing seals to determine which will be a best choice/fit.
     
  6. 166&456

    166&456 Formula 3

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    #6 166&456, Sep 5, 2011
    Don't forget to re-seal the splines that connect the hubs to the spider gears when re-installing them, otherwise you'll still have a leak, just in a different spot.
     
  7. smg2

    smg2 F1 World Champ
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    #7 smg2, Sep 5, 2011
    Yep, Timken 1012N usually less than $5. available most anywhere in the US as it's shared with the jeeps of the similar era.
     
  8. chairpilot

    chairpilot Formula 3

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    #8 chairpilot, Sep 5, 2011
    I never had these apart so I'm no following you exactly. But I'm sure I'll be able to figure it out when I do it, yes? What do I use for the sealant?
     
  9. chairpilot

    chairpilot Formula 3

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    #9 chairpilot, Sep 5, 2011

    Great thank you!
     
  10. Brian Harper

    Brian Harper F1 Rookie
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    #10 Brian Harper, Sep 5, 2011
    Note that the seal in the horsey box for 8x the price is allegedly viton. The other seals in the same size from generic sources are probably buna or whatever rubber. I don't think anyone would argue that the viton seal is superior in this application.

    That said I used the $5 seal from the local bearing supplier on one side and a seal from the local auto parts store on the other side. Counter guy said it was the size of the front wheel bearing for a Porsche 944. I suppose that if the seal can deal with disc brake heat it should be fine with the diff.
     
  11. smg2

    smg2 F1 World Champ
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    #11 smg2, Sep 5, 2011
    the timken seal is available as viton and I do believe that it's oem application is the diff seal for porsche, audi, bmw and many more. helps to have the timken reference spec catalog. been using them for yrs for those not wanting the horsey box part. my personal mondial has them in for the last 30k+ miles with zero leak issues.

    flange sealant or anaerobic sealant on the threads of the bolt will keep the oil in the diff. It's under pressure on the mondials due to the gearbox oil pump.
     
  12. smg2

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    #12 smg2, Sep 5, 2011
    Last edited by a moderator: Sep 7, 2017
  13. Brian Harper

    Brian Harper F1 Rookie
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    #13 Brian Harper, Sep 5, 2011
    Excellent! I could not find a cross ref for that seal in viton when I did my diff seals a couple of years ago. Is the Timken viton version still $5-$10?
     
  14. smg2

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    #14 smg2, Sep 6, 2011
    Timken # 710078 is a 470 V that's an exposed metal case with a dust seal and single spring lip in Viton.
     
  15. chairpilot

    chairpilot Formula 3

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    #15 chairpilot, Sep 18, 2011
    The seals were hard as a rock! New ones are on the way. What do I torque the center axle bolt to?
     
  16. chairpilot

    chairpilot Formula 3

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    #16 chairpilot, Sep 19, 2011
    I checked on the Timken 1012N specs and it is 45mmx62mmx8mm thick. The old seal is 10mm thick. Should that matter? So far I cannot locate a 10mm thick version. Do any of you know of another part number that is 10mm and inexpensive?
     
  17. chairpilot

    chairpilot Formula 3

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    #17 chairpilot, Sep 19, 2011
    I found the replacement diff seal: the Mercedes part number is 003 997 93 46.
     
  18. viphoto

    viphoto Formula Junior

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    #18 viphoto, Sep 19, 2011
    I don't know if it matters but the original seals were rubber encased and the wheel seals are metal housings. Not sure if being mounted in aluminum matters but I though I saw somewhere that it was supposed to be a coated for that reason. BTW I bought one of the nitrile coated ones from GT parts in Az and it was about $26 before shipping.
     
  19. chairpilot

    chairpilot Formula 3

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    #19 chairpilot, Sep 20, 2011
    The Mercedes seals I know have in hand are metal case. Who knows if nitrile coated ones are really necessary?

    Bob
     
  20. viphoto

    viphoto Formula Junior

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    #20 viphoto, Sep 21, 2011
    I have been racking my brain trying to remember where I saw mention of the rubber vs metal seals...I found this today online ...about 3/4 the way down the page it talks about rubber vs metal... That being said I think a number of people used the metal ones with no problems...but the article makes a good case for the rubber ones.

    http://www.rlhudson.com/shaft%20seal%20book/design-anatomy5.html
     
  21. chairpilot

    chairpilot Formula 3

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    #21 chairpilot, Sep 21, 2011
    I'm probably going to RTV the outer seal surface and inner diff case surface and call it good.
     

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