Leaky 727

Discussion in 'Transmission and Drivetrain Tech' started by Gandy Dancer, Jan 12, 2018.

  1. Gandy Dancer

    Gandy Dancer Well-Known Member

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    Hello FABO - I have installed a rebuilt 727 in my 66 Barracuda. Mounted to a 318. When I removed my 904 it never had any issues with leaking at the dipstick tube. I am now having leaks occur at the dipstick and I cannot seem to prevent the leaks. I've tried RTV red, and it did not work.

    Does anyone have any recommendations or ideas on how I can prevent a leak at the dipstick. And unfortunately like the 904 there is no bolt hold to fasten the dipstick to the transmission.

    Thanks!!
     
  2. Plymouth 65

    Plymouth 65 Floorable Deplorable

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    Did you use a new o-ring also? 65'
     
  3. joshcook81

    joshcook81 Well-Known Member

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    My 727 dipstick tubed leaked, I pulled it out and changed the O-Ring, hasn’t leaked since :)
     
  4. 70Duster440

    70Duster440 Well-Known Member

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    As mentioned: fresh o-ring. Be sure to clean all the RTV off and don't use it. Then figure out a way to secure to tube so it doesn't flop around.
     
  5. 1994redram

    1994redram FABO Gold Member FABO Gold Member

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    I always clean it up really well and put A fresh O-ring on it with a thin coating of RTV. Always worked great for me. The dipstick tube has to have a way to bolt it on. Without it bolted up and mounted correctly, the fluid readings will be off. The dipstick tube will sit too low into the trans.
     
  6. forphorty

    forphorty Well-Known Member

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  7. iScamp

    iScamp Well-Known Member

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    I might be missing something here in the conversation but.... you're saying there is no tab spot welded to the dipstick tube? That tab would be secured to one of the bellhousing bolts. (in most instances)
     
  8. Demonic

    Demonic Well-Known Member

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    Also, make sure you have the correct o ring. Too thick and you'll never get it seated, too thin and it will leak again.
     
  9. 70Duster440

    70Duster440 Well-Known Member

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  10. Gandy Dancer

    Gandy Dancer Well-Known Member

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    Excellent! I will take these recommendations and revisit my dipstick. I may start fresh with the Mancini dipstick. That looks rather promising.

    Thanks!
     
  11. d55dave

    d55dave Well-Known Member

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    Somewhere around 66 and earlier 727s have a 90 degree tab welded to the bottom of the tube that bolts to a tapped hole on the trans housing adjacent to where the tube goes in. They also have a tab that bolts to one of the bellhousing bolts. 67 (I think) and later only have the tab for the bellhousing bolt.

    Regardless, it is important to pre fit the tube and ensure that, when the tab(s) are bolted up, the bottom of the tube isnt pre loaded. Once you have determined this, use a new o ring, wipe everything down good with lacquer thinner or brake clean (including the ID of the trans case that the tube fits into), use a reasonable (not excessive) amount of good sealant such as oil resistant rtv under and on the o ring, insert the tube and tighten the mounts. Let the sealant cure before adding oil.

    This is usually something that I do as a last step, once the trans is in, the mount is on and everything is tight, to avoid tweaking the tube. I also use my finger and put a bead of sealant around the tube to trans case interface.