Oil pan gasket

Discussion in 'Oil' started by Dark Horse, May 12, 2017.

  1. Dark Horse

    Dark Horse Member

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    FullSizeRender.jpg Hi guys.
    On the 103 cu.in. Dyna engines , as I understand it , when draining the transmission fluid , the fluid actually has to pass down through a hole cast in the engine oil pan in order to reach the drain hole.
    Obviously , where the oil pan is bolted to the gearbox casing , there is a gasket , but I've noticed that the gasket does not extend to seal around this hole where the transmission fluid passes out of the transmission casing 'through' the oil pan .
    My question is , what stops the engine oil / transmission fluid leaking into each other at this point ?
    There is a tab on the oil pan gasket to seal around the hole at the front of the pan ( which is blanked off by a plug screwed into the front of the pan) but not where the draining transmission fluid goes down the hole in the side !
     
  2. dolt

    dolt Senior Member

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    I have not had the opportunity to R/R the oil pan from a Dyna but I expect the mating surfaces between the transmission case and the oil pan at that particular location fit tight enough together that the trans fluid cannot escape into the oil pan. Gaskets in the earlier 88" motors are exactly the same. I am pretty sure that this is not an oversight on the MoCo engineers since all the TC gaskets between transmission case and oil pan are the same, regardless of motor size.

    I know you have previously posted on the mystery of the missing transmission fluid that seems to evaporate from your transmission since there is no sign of a leak but the fluid dramatically disappears. If it was leaking into the oil pan at the rate you have previously described you would know it because you would start seeing blow by through the head breathers due to the excessive oil in the oiling system. As I and others have posted in your previous posts, fluid disappearing at the rate you describe with no evidence of a leak is unexplainable.;)
     
  3. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

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    My guess would be an O ring where the 2 come together.
     
  4. Dark Horse

    Dark Horse Member

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    IMG_2383.JPG
    Thanks for your replies guys !
    I've since found out that the gasket (26072-99) shown in my original diagram , is obsolete !
    The newer one (26072-99A shown above ) has an extra 'tab' included to cater for the transmission fluid drain hole.
    Thanks once again for all your help guys !
     
  5. Jeff Klarich

    Jeff Klarich Experienced Member Contributor

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    Thanks for the clarification, I couldn't believe the MoCo wouldn't use some kind of a gasket or O ring where 2 different fluids could have the potential of coming together.
     
  6. Dark Horse

    Dark Horse Member

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    I agree ! The only reason I thought that this must be the case is because the part computer in my official Harley dealership showed the older gasket with no tab !
    Even the mechanic was surprised and thought maybe they used a smear of RTV silicone during assembly.
    You'd have thought a main dealer would have the very latest part number !