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Hot Rods 9" Ford Third Member - New Gasket Is Leaking Gear Oil

Discussion in 'The Hokey Ass Message Board' started by davvet2, Aug 17, 2023.

  1. davvet2
    Joined: Mar 18, 2006
    Posts: 162

    davvet2
    Member

    Finally got a good used posi 3:70 third member for the 9" in my 32. Bought a FelPro gasket for it, put yellow glue on the housing and also on the gasket, waited for it to tack up and slipped the gasket over the studs in the housing. Then took black silicone and ran a ring of sealant around each stud.
    Fought with the third member for a while, but finally got it to slide on the studs and bottom out.
    I bought new lock nuts and copper washers, installed them and gradually tightened them up in a criss cross pattern. When I was sure they were tight, I filled the housing with 2 1/2 quarts of gear oil. (This third member doesn't have a fill plug, so I had to use a 5' hose with a funnel and go thru the axle tube into the center of the housing). Went inside for a while to cool off, came back in the garage to find a large puddle of gear oil on the floor, the leak is from the bottom of the third member. Tried tightening up on the bolts, but it still leaked.

    After sopping up most of the oil on the floor, I removed the third member to look at the gasket.
    Taking a razor s****er to the gasket, I realized that it was stuck pretty well to the housing, and the silicone was stuck well, too. The housing is powder coated, and I still have to get the gasket completely s****ed off.

    I don't know what happened here, the gasket I bought was for a 66 - 86 Bronco 9", and the new one I bought today is for a 68 -76 Ford Torino 9". I have no clue what the housing that was installed in the car came from. I don't know what the difference in the gaskets would be, but thought I'd try another part number in case the first one was the wrong part.

    Ideas?

    Thanks,

    Jim
     
  2. 57 Fargo
    Joined: Jan 22, 2012
    Posts: 6,182

    57 Fargo
    Member

    I’ve never used a gasket with any removable carrier differential. I just use sealer.
     
    CSPIDY likes this.
  3. chevyfordman
    Joined: Oct 4, 2008
    Posts: 1,512

    chevyfordman
    Member

    What sealer worked the best for you?
     
  4. Dedsoto
    Joined: Jan 7, 2014
    Posts: 375

    Dedsoto
    Member
    from Australia

    I use a paper gasket with a thin smear of silicone on each side, clean surfaces on both the housing and third member. copper or aluminium washers without sealant. For those without fill plugs install one axle then jack the other side right up and tip it in the tube.
     
    INVISIBLEKID and Algoma56 like this.
  5. dalesnyder
    Joined: Feb 6, 2008
    Posts: 647

    dalesnyder
    Member

    Just a thin smear of ultra black, no washers or gaskets. The one time I used a paper gasket it leaked too.
     
    CSPIDY, Nailhead Jason and Algoma56 like this.
  6. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    Housing is powder coated? I'd look at it real close to make sure all the coating is off the gasket surface and studs.

    Paper gasket and some non hardening sealer like Permatex Aviation should work fine.
     
    RICH B, alanp561, jimmy six and 3 others like this.
  7. davvet2
    Joined: Mar 18, 2006
    Posts: 162

    davvet2
    Member

    I've been rethinking installation of the paper gasket, and I seem to remember that the holes for the bottom studs were a little bit off. I thought that the silicone sealer would make up the difference and seal it up OK. Looks like that was wrong. The housing and studs are powder coated, and that will need to be removed. I plan to use Gasga cinch on the new gasket that I had to order.
     
    jimmy six and Algoma56 like this.
  8. 427 sleeper
    Joined: Mar 8, 2017
    Posts: 3,367

    427 sleeper
    ALLIANCE MEMBER

    GM head gasket sealer is my go to for all questionable area's. Which is basically Permatex aviation sealer. ;)
     
    Algoma56 likes this.
  9. Boggus Deal
    Joined: Dec 27, 2012
    Posts: 27

    Boggus Deal
    Member

    Since this sounds like a bit of a conglomeration of parts, you need to make sure the housing is vented and the vent is not obstructed. Heat will build up and will push the gear oil out somewhere. Clean the housing and the pumpkin mating surfaces to bare metal put a THIN smear of silicone on the gasket, use copper washers, like Ford did when they designed the axle, and you should be good.
     
  10. davvet2
    Joined: Mar 18, 2006
    Posts: 162

    davvet2
    Member

    Thanks to everyone that responded to my problem. I now have several options.

    Jim
     
  11. jaracer
    Joined: Oct 4, 2008
    Posts: 3,046

    jaracer
    ALLIANCE MEMBER

    Before I put it back together I would fill the housing as full as I could get it with the third member out and make sure the leak wasn't a housing problem. I would also take a real close leak at the third member housing around the bottom. From the amount you leaked the cause should be easy to see.

    Back in the day I did a lot of 9 inch rears at the Lincoln/Mercury dealership. I remember the Ford gasket being a bit different than just paper. I'm thinking it was a composite gasket. I never used any sealant and didn't have leaks.
     
  12. chevyfordman
    Joined: Oct 4, 2008
    Posts: 1,512

    chevyfordman
    Member

    For all those that used gaskets long ago, can we still get any good gaskets anymore?
     
  13. bobss396
    Joined: Aug 27, 2008
    Posts: 18,739

    bobss396
    Member

    I used the paper gasket, I hit one side with Permatex spray first, to keep it ****ed down to the housing. Not a drop of a leak since. I used new copper washers and nuts.
     
    INVISIBLEKID likes this.
  14. Those housings often have the back cover,and axle tubes welded to the center area.If a cracked weld is covered by powder coat it could be leaking. If the next gasket/ sealer doesnt fix it then consider leak checking with solvent. Take a small straight edge,and check the gasket surfaces for any low spots. Check the carrier surfaces too.Just because its machined cast doesnt mean it cant have a low spot.
     
    Boneyard51 and Algoma56 like this.
  15. onetrickpony
    Joined: Sep 21, 2010
    Posts: 859

    onetrickpony
    Member
    from Texas

    I used a Felpro gasket last week when I swapped mine. Thin RTV on both sides and reused the copper washers after annealing them. No leaks so far.
     
    Algoma56 likes this.
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    FelPro gaskets still work, eh? I haven't had any issues with them. I put one in the Corvette a couple weeks ago, not a drop
     
    Truckdoctor Andy and alanp561 like this.
  17. thecj3man
    Joined: Aug 16, 2010
    Posts: 82

    thecj3man
    Member
    from TN

    I used a lube locker gasket on the 9" in my car. It has survived a couple third member changes so far. It was expensive to start with, but not cleaning RTV off was worth it to me.
     
    irishsteve likes this.
  18. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    If you're going to swap centers often, use sealer (not rtv) between gasket and housing, and smear some grease on the gasket where the center sits on it. It will last through several changes.
     
    alanp561, X-cpe, vtx1800 and 2 others like this.
  19. jimmy six
    Joined: Mar 21, 2006
    Posts: 17,063

    jimmy six
    ALLIANCE MEMBER

    Sounds like you need to hammer all the studs inside and remove the powder coat on the gasket surface and check it for flat. I’ve never seen or heard of anyone coating it. I use Permatex #2 on the pumpkin side of a gasket so it’s easier to get off. None leak
     
    bobss396, alanp561 and Tman like this.
  20. VOODOO ROD & CUSTOM
    Joined: Dec 27, 2009
    Posts: 1,313

    VOODOO ROD & CUSTOM
    Member

    Ford 9" Rears are like Old Harley Davidsons; they like to mark their territory !
    Silicone is the only way I've got a Ford 9" to stop leaking.

    Happy Sealing,
    VR&C.
     
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  21. blue 49
    Joined: Dec 24, 2006
    Posts: 2,126

    blue 49
    Member
    from Iowa

    I may never get it off again, but I used the Right Stuff, no gasket on the aluminum cover I put on my 8.8. Still dry as a bone after about a year.

    Gary
     
    bobss396 likes this.
  22. swade41
    Joined: Apr 6, 2004
    Posts: 14,474

    swade41
    Member
    from Buffalo,NY

    I used gaskets and "the right stuff" rtv on these two and no leaks

    Screenshot_20230818_234412_Gallery.jpg Screenshot_20230818_234713_Gallery.jpg

    The Henry J I got a little over zealous with the blue rtv 10 yrs ago, but again no leaks ....... but I swear there's a leak on the backside of the housing where I circled

    000_0042_zps3d90d2cf.jpg Screenshot_20230818_235550_Gallery.jpg
     
    AHotRod likes this.
  23. gimpyshotrods
    Joined: May 20, 2009
    Posts: 24,516

    gimpyshotrods
    ALLIANCE MEMBER

  24. onetrickpony
    Joined: Sep 21, 2010
    Posts: 859

    onetrickpony
    Member
    from Texas

    For housing seepage after ***embly, I use epoxy putty. I prefer the blue/yellow stuff but JB Weld makes one, too. Wipe the area with thinner then smear some in the leak. You can sand it down after it dries. Touch up the paint and done.

    It works for seeping oil pans and gas tanks, too.
     
    swade41 and chicken like this.
  25. davvet2
    Joined: Mar 18, 2006
    Posts: 162

    davvet2
    Member

    The new gasket came today, and it's the correct one, all the holes line up.
    I stripped the powder coating off the housing, and am now looking at bare metal
    on the third member as well.
    I ***ume that I need to put a light coat on the housing and spread it with my gloved finger; how long do I wait before sliding the gasket over the studs and press it down flat on the housing? Then, I put a similar coat on the gasket, with an RTV ring around the studs and how long do I wait before installing the third member? Do I need to put RTV on the third member sealing surface as well? Also, how do I make sure the third member is completely seated, all the way down?
    After snugging up the locknuts with fresh copper washers, how long do I wait before cranking them down?
    After that, how long do I wait before filling it with oil?

    I'm asking all these questions because I don't want a repeat of what happened last time.

    Thanks, Jim
     
    Last edited: Aug 21, 2023
  26. squirrel
    Joined: Sep 23, 2004
    Posts: 59,932

    squirrel
    Member

    RTV? ugh.

    There should be no need to use any sealer on the studs if you use copper washers.

    I have no leaking issues using permatex aviation sealer on the bottom half of the gasket, both sides, and new copper washers. But I'm RTV phobic, so maybe don't listen to me? Ford did not use RTV on them from the factory, and they did not leak.
     
    bobss396, 427 sleeper and alanp561 like this.
  27. NJ Don
    Joined: Dec 25, 2019
    Posts: 261

    NJ Don
    Member

    Just get a "Lube Locker" gasket ...done!
     
  28. alanp561
    Joined: Oct 1, 2017
    Posts: 5,543

    alanp561
    ALLIANCE MEMBER

    Here ya go.

    upload_2023-8-21_19-37-52.png
     
  29. alanp561
    Joined: Oct 1, 2017
    Posts: 5,543

    alanp561
    ALLIANCE MEMBER

    Sorry, I tried to include this as well but it didn't want to go. upload_2023-8-21_19-40-47.png upload_2023-8-21_19-40-47.png
     
  30. Moriarity
    Joined: Apr 11, 2001
    Posts: 37,453

    Moriarity
    SUPER MODERATOR
    Staff Member

    If you must use RTV only the thinnest possible finger smear on both surfaces and NO rings of rtv around the studs. put it together while it is still wet. waiting for it to cure before hand will make it leak. The copper washers will seal the studs
     

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