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Never-ending 727 Transmission leak!!!

Discussion in 'The Hokey Ass Message Board' started by 62dartman, Nov 17, 2011.

  1. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member

    Hey guys, i have a 1962 Dodge Dart that has had a tranny leak for probably 7 years now!!! I know right!! I let it run low one too many times about 5 years ago and blew the trans.. So when i rebuilt it i made sure to change all seals including the shifter shaft (manual valve shaft) which was the original leak, but the leak came right back. So my question is -is there a bushing of some type of that shaft because it seems to move side to side excessively(didnt notice when i had it out). Any guidance would b appresheated, Thanks
     
  2. 54pumpjack
    Joined: Nov 2, 2005
    Posts: 66

    54pumpjack
    Member

    When does it leak? I mean does it leak when it sits for a period of time or leak all the time? Mopar trannys are common to leak when they sit for a period of time because of convertor drain back, if there driven daily this usually doesn't happen. Hope maybe this sheds a little light or helps open up the beginning of getting you fixed.
     
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  3. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member

    Yeah it leaks every night. She's my daily driver and i see the same little puddle every morning or every night when i leave work. Just keep fillin and driving!!!
     
  4. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,912

    need louvers ?
    Member

    The condition 54 pumpjack was refering to is real common with 727s. The seal that seals the converter as it slides into the pump on the front of the trans is usually the culprit. It's also the one no one ever changes. When it is intermitant like above, it's when the seal is on it's way out. When it just dumps every day and night, it's just bad. The converter drains back into the pan and suddenly you have about two extra quarts of juice in there, and on start up most pumps back into the converter, but some finds the easy ways out. Most common "easy ways" are the shifter shaft, vents, and fill tube seals. Fix any or all of those all you want, but if you don't drop the trans and do the seal it'll hapen again.
     
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  5. swe64
    Joined: Nov 22, 2010
    Posts: 415

    swe64
    Member

    i was suprised when i took drivshaft out an found a wery little hole in yoke i weled the hole and did not leak from rear anyway
    ken sweden
     
  6. b-body-bob
    Joined: Apr 23, 2011
    Posts: 357

    b-body-bob
    Member

    I'm confused here - what does fixing the front seal in the trans have to do with stopping the converter from draining back and overfilling the transmission to the point of leakage?
     
  7. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,724

    stealthcruiser
    Member


    Standing by as well.
     
  8. coolbreeze1340
    Joined: Aug 18, 2009
    Posts: 1,342

    coolbreeze1340
    Member
    from Indiana

    I don't think it stops the drain back issue and it is not the front seal that everyone thinks.
     
  9. tooljunkie
    Joined: Oct 18, 2010
    Posts: 209

    tooljunkie
    Member
    from manitoba

    a worn valve body could be the issue here.the shift shaft could be pushed to one end due to shift rod adjustment.
    try blocking wheels and parking it in neutral ovenight.
    there might be a redi-sleeve available for a shaft this size,im unsure.
    a new shaft may help,if its worn.

    i have seen the torque convertor crack on more than one occasion,but thats a bellhousing leak.
     
  10. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,912

    need louvers ?
    Member

    It keeps atmospheric pressure from pushing the fluid down out of the converter. Works on the same principal as holding a cup under water, keeping the rim under the water flipping it over and pulling it towards the waters surface. You have a cup full of water above the surface as long as you keep the open end submerged. Bring the open end above water and all the water "falls" out. Same deal with your converter. when the coverter fills with fluid, if there is no "leak" to atmospheric pressure, it stays in the converter. Break the seal and all the fluid runs down into the pan.
    727s are more susceptible to this problem than most, but ford C4 have it as a common problem too. I found this out the hard way with mine. I'm obsessed with killing leaks, and after resealing my 727 a billion times, an old trans guy asked if I did the converter seal. Gave me the same expanation as I just gave, and damn if he wasn't right! There is always the other way... I yanked the damn automatic and stuck in a Tremac 5 speed and made the car more fun to drive, quicker, faster, and almost doubled the MPG.
     
  11. brandon
    Joined: Jul 19, 2002
    Posts: 6,313

    brandon
    Member

    My old valiant had a slight leak that ended up being a small crack...it leaked when ever it sat still....lol
     
  12. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    Many people install the shaft seal backwards.
     
  13. stealthcruiser
    Joined: Dec 24, 2002
    Posts: 3,724

    stealthcruiser
    Member

    Thanks, Brother.........Could you elaborate a little more, please?
    At first I was thinking converter snout lip seal.........Then pump to case seal.............Where is the one you speak of located please Sir.
     
  14. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,912

    need louvers ?
    Member

    It's been awhile since I did this one, but I believe it was what you are calling converter snout lip seal. Should fit right inside the pump and register on the converter. Sometimes the converter has a groove worn in it that is bad enough that the new seal won't, then it's time for a new converter.
     
  15. 50dodge4x4
    Joined: Aug 7, 2004
    Posts: 3,536

    50dodge4x4
    Member

    I had a leak in the 727 in my 54. Found the leak at a shaft/ casing where the tail housing bolts onto the case. Just off center (driver side, I think), just above the pan rail, there is the end of a machined shaft that comes through the front case that is about 5/8" in diameter. There is no seal or bushing there I could see, looks like the case & the shaft are suppose to seal. Mine would leak a few drops while the engine was running, would run onto the pan gasket and around the both sides of the pan. When ever you stopped moving, the fluid would pool to whichever side or corner was lower and create a spot on the ground about 2"-3" in diameter. The only time it leaked was when the engine was running (in my case), but it would only drip after the truck stopped moving for a 1/2 hour. If the pan was level when parked, it would drip down the bellhousing. Unless the truck was parked in the same location, facing the same direction, the puddle would move around the trans. Don't know what the fix would be, sold the truck before I got into it. Gene
     
  16. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member

    Thanks for the plethora of info here. Im still leaning towards the shaft/valve body bushing thing, kinda like tooljunkie is talking about, but im mainly wondering if there is some kinda bushing/sleeve for this cause i cant find one online and dont remember if there was one in there when i rebuilt it. But when i rebuilt it i def changed every seal in the kit because i had leakin issues before then. And i had my local trans guy press in a new frt pump bushing as well and replaced the converter.
     
  17. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member

    its a good thing i get my tranny fluid for free or else id b broke!!!lol!
     
  18. b-body-bob
    Joined: Apr 23, 2011
    Posts: 357

    b-body-bob
    Member

    There's an o-ring on that shaft. It's the pivot for the rear servo arm. See video
    http://www.youtube.com/watch?v=rXtcTIGfdY4&feature=related
     
  19. 77powerwagon
    Joined: Oct 22, 2010
    Posts: 45

    77powerwagon
    Member

    I have 2 727 out of a 77 military powerwagon one is in the truck and one was rebuilt by the army and came with truck. If your interested let me know. gonna have to change output shaft though seeing as a transfer case was bolted to it. Oh and I have a new torque converter for it too. I'm just over the bridge from ya.
     
  20. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member



    Well thanks for the offer man, but im not sure i wanna rip this one back out yet. Also not sure if one that "new" would b the same as mine, with the pushbutton and all?? Them power wagons are pretty cool trucks though!!
     
  21. Bonneville Avanti Dan
    Joined: Jan 21, 2011
    Posts: 243

    Bonneville Avanti Dan
    Member
    from California

    Been building them for over 40 years. The problem you have is common. There are two seals on the shaft. There is a seal that looks like a small wheel seal that seals the selector shaft at the case and is pressed into the cae. The other is at the top of the tower and it seals the throttle pressure shaft. If you can move the selector shaft back and forth then the valve body and or selecotor housing are worn. They move everytime the shifter does so they are prone to egg shape wear. Remove the pan and the valve body. Pull the clip and slip the throttle body shaft out. Then make sure you contain the selector shaft ball as it is spring loaded and will shoot out. Take the housing out of the valve body and look at both parts. I have found that most of the time the valve body part is in OK shape. I go to my local trans shop and buy a new selector housing. That usually takes the play out of the system. Install a new seal and put it back together. Even if the convertor drains back it should not leak. Hope this helps.
    Dan
     
  22. 62dartman
    Joined: Feb 24, 2010
    Posts: 174

    62dartman
    Member


    That's what i was thinking, it should still hold fluid. This seems right on as far as the direction that im looking to go in. I just did some side work (electrical)for an old school trans guy near my dealership so im gonna cash in some of those favors and see if he can tighten up/replace that shaft like u were saying. Appreciate the help guys, she's my daily driver so i havent got a window of opportunity where i dont need her long enough to dismantle her!!!
     
  23. moparjack44
    Joined: Nov 8, 2005
    Posts: 467

    moparjack44
    Member

    Better late than never, I hope.
    I had a leak, I thought it was drain plugs on the extra capacity Moroso tranny pan. Replaced with stock pan, still leaking.
    Here is how I replaced the pan;
    1. Drained fluid. Could not find gasket I wanted, so I ordered.
    2. It drained for about 30 hours, waiting for new gasket.
    3. Received and installed new "reusable" gasket and new filter, and stock volume tranny pan.
    4. Added " 5 " quarts of tranny fluid. Still leaking?

    My question is, how much possibly drained during that 30 hour waiting/draining period? My converter holds 5 quarts. Did the 5 quarts I added over fill and create the leak? If possible, how do I confirm?

    Jack
     
  24. greybeard360
    Joined: Feb 28, 2008
    Posts: 1,348

    greybeard360
    Member

    Shift shaft seal is a common leak on those and Bonneville is dead on... The problem is where the shifter detent pivots on the valve body. TransGo makes a kit for the valve body to prevent convertor drainback. That problem has nothing to do with the pump seal. Some people will believe anything.

    I too have built a couple of hundred TF's over the years. They have some quirks but are very stout tranny's. If you know what to watch for when you take them apart, building one that works great and doesn't leak is easy.

    BTW.... Make sure there isn't fluid leaking from the filler tube oring. That is another common leak spot. If you had to push the tube to the side to get the bellhousing bolt to go thru the mount strap, the strap is bent. It should fit right in place and the bolt slide right thru it into the block. Any flexing you do to make it fit distorts the oring and it will never seal.

    Sent from my Moto G Play using The H.A.M.B. mobile app
     
  25. moparjack44
    Joined: Nov 8, 2005
    Posts: 467

    moparjack44
    Member

    I forgot to mention, I did NOT officially drain the converter. It just "dripped" for about 30 hours with the pan off while waiting for new gasket?

    Jack
     
  26. radarsonwheels
    Joined: Dec 15, 2006
    Posts: 167

    radarsonwheels
    Member
    from Philly

    Just run it a few minutes in neutral and check the dipstick. Easy!

    If you have a tf2 kit you can run it in P and it’ll fill the converter
     
  27. gene-koning
    Joined: Oct 28, 2016
    Posts: 1,372

    gene-koning
    Member

    Moparjack44, Its pretty typical for the Mopar autos to drain back the fluid in the torque converter. It can drain back about 1/2 of the converter capacity, and often does so after sitting as little as 8 hours. The cause of this is in the valve body, and as stated, there are companies that make parts to cure it.
    That said, the trans is suppose to be sealed so it doesn't leak, even with the extra 2 1/2 quarts of ATF in the pan that has drained from the converter.
    The shift seal, and the dipstick are pretty normal location to leak. Both will drip down onto the oil pan and make it look like the pan gasket is leaking. I've also seen the park/neutral switch leak. Basically any gasket or seal within about 5" of the bottom of the pan can and has leaked at some point.

    After the trans gets sealed, after any start up where the trans has sat idle for more then a few hours, I always shift it into neutral for about 30 seconds so the pump can refill the torque converter, before I put it into drive or reverse. I do this because the Mopar transmissions do not pump fluid in park, so when it is in park, it will not refill the converter. That gives you a lot of wear before it can fill the converter once you put it into drive or reverse. Until the converter is refilled, the trans will slip badly if you simply put it in gear and expect it to go. Gene
     

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