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700r4 backflow problem.

Discussion in 'The Hokey Ass Message Board' started by mixmaster-meat-wad, May 29, 2012.

  1. mixmaster-meat-wad
    Joined: Apr 3, 2011
    Posts: 59

    mixmaster-meat-wad
    Member

    Hey guys. Wanna save me some cash?

    Here is my delima. This is my first auto transmission in a build. I Stole a 700r4 out of a late model transam. Its been a year probably and finally got my truck going last week. When the truck sits more than a day i get a huge puddle of tranny fluid under my truck. I get the truck up and running, fluid levels good, but once it sits it backflows into the pan. The only think i can think of is maybe i needed a "backflow switch" in line with my inter-cooler. I didnt think i even needed one but now im thinking i do. If i do need one which line do i put it in so i dont have it backwards and starve the tranny of fluid unintentionally.

    Any advice would be great.
     
  2. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    You likely just have a simple leak.
     
    TA DAD likes this.
  3. newsomtravis
    Joined: Jun 1, 2009
    Posts: 562

    newsomtravis
    Member
    from pville, ca

    never heard of such a thing, backflow valve, hmm.......sounds like a leak, a few drops of atf can look like a huge puddle.....
     
  4. are you sure you have the right dipstick?

    sounds like a possible overfill problem. (overflow due to heat expansion)

    never heard of a 'back flow' problem. system capacity is just that unless your cooler is gigantic and mounted 3 feet above your tranny.

    but yeah, could just be a simple leak.

    possible leaks:
    TV cable
    Dipstick tube
    pan
    output shaft seal
    convertor hub seal
    manual shaft seal (gear selector)
    speedo housing seal

    unless you have a split case, thats it.
     
    Last edited: May 29, 2012

  5. Grumbler
    Joined: Mar 2, 2009
    Posts: 358

    Grumbler
    Member

    I had a puddle of fluid from my 200R on the floor every morning. It was the O ring on the electrical connector on the side of the case.
     
  6. 1959apache
    Joined: Nov 22, 2009
    Posts: 2,635

    1959apache
    Member

    I have a similar problem, when the atf is running through the cooler everything is hunky dory (at the correct level), but when you shut it off it wants to drain to the pan. If you let it sit for a while it will leak from everywhere as if it were overfull (which it is now that it isnt running); I know your problem. Are you using the standard stamped tranny pan? I bought a thick pan (1/4 flange that the bolts go through) with a drain plug in the bottom. This solved a lot of my problem. Also check the dipstick o-ring (the standard o-ring that came with the tranny probably needs to be replaced). I also used a flexible dipstick and this solved the leak (better oring design). I only rarely have a leak and it is only when I don't run the truck for quite a while (seals expand when they get hot). How long has yours been sitting?

    Pictures of it on my build thread page 20:

    http://www.jalopyjournal.com/forum/showthread.php?t=447466&page=20
     
    Last edited: May 29, 2012
  7. My coupe has been leaking at the trans dipstick for years. Itnhas a lokar flexible tube. Transmission guy says the fluid level rises when the fluidndrains back from the torque converter. I plan to address this leak with a GM dipstick tube..
     
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  8. greg32
    Joined: Jun 21, 2007
    Posts: 2,230

    greg32
    Member
    from Indiana

    I had the same issue on a turbo 400 and a 700. Junk Lokar dipstick. Take it out, new O ring, and silicone around O ring. Problem solved. Also check the tv cable, a little silicone there also.
     
    olscrounger likes this.
  9. mixmaster-meat-wad
    Joined: Apr 3, 2011
    Posts: 59

    mixmaster-meat-wad
    Member

    Ill run the truck all day. Running around taking it through its paces. I will continually check the fluid levels until the fluid gets hot to get a good HOT reading like i want. But once the tranny sits a day or two then i will check again and it will have a crazy ready off the charts like i dumped 5 quarts to many or something.

    I checked out the O ring on my dipstick and its all nasty like what alot of you guys are saying. Im going to have to cut the stock tube off since its been welded down to a very inconvenient spot for me to screw with. Looks like im gonna have to do it though.

    It doesn't sound like this will fix the problem though. It will only mask it. Should it back-flow at all? Or is it all because the 1 O-ring on my dipstick?
     
  10. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I may be mistaken, but it seems to me that there is such a thing as 'converter leakdown'........when running, the converter is full of fluid...when shut down I believe that fluid is supposed to remain in the converter and there is some internal check valve to accomplish that. When that malfunctions, the converter leaks some, or up to 1/2, of the fluid back into the trans case which raises the internal level enough to leak out any available place.....dipstick base seal, shift shaft seal, up the dip stick tube, etc.

    Ray
     
    bchctybob and olscrounger like this.
  11. You could try a new pan gasket.
     
  12. I don't know much of anything about automatics but I have C4 trans that does the same thing only it runs out of the vent tube in the top of the trans if it sets a day. I asked a transmission guy and he asked if the transmission had set unused for a long time after being used and I told him it sat for several years after being rebuilt and run for a year or two. He told me it sounded like the converter was leaking back into the trans and it probably had a dried out seal from sitting. I don't know what seal, but it sounds plausible to me.
     
  13. In almost any automatic nearly all the fluid drains back into the pan, and that is more than the pan holds. If the opan gasket is bad or isn't making a seal it is going to bleed all over the floor when it is not in use.

    Now out the vent pipe is an entirely different story, there should not be enough fluid in the transmission to reach the vent tube. I would be sure that I had the correct dip stick and was checking the fluid level properly.
     
  14. mixmaster-meat-wad
    Joined: Apr 3, 2011
    Posts: 59

    mixmaster-meat-wad
    Member

    @Hnstray-Good call on the "converter leakdown". Ill have to try and find an honest tranny shop around town. I went to AAMCO who treats most their customers like asses when their not to tranny savvy. AAMCO did go ahead and bill me 300 bucks for doing a whole lot of nothing though.
     
    olscrounger likes this.
  15. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    Are you checking the fluid level running, or off?
     
  16. mixmaster-meat-wad
    Joined: Apr 3, 2011
    Posts: 59

    mixmaster-meat-wad
    Member

    I check it continuously. Once i know i can get a good HOT reading after a decent drive then i check it and Fluid level is great Once it sits a day or two ill check it cold and it will read way way high like i over filled it. But once i start my truck up, put it through the gears and then check it. The fluid level is back to normal again.
     
  17. need louvers ?
    Joined: Nov 20, 2008
    Posts: 12,903

    need louvers ?
    Member

    I have no experiance with 700r4s, but what you describe has a 50/50 chance of happening with Mopar 727s. There is a seal in the pump body that rides on the coverter snout on those that when replaced, the problem is solved. I'm not sure if that is present on a 700r4, but I'd check.
     
  18. VSO737
    Joined: Aug 24, 2005
    Posts: 237

    VSO737
    Member

    I don't know about the 700R4 BUT I can tell you that a 1957 Cast Iron 2 speed POWERGLIDE will drain back from the TORQUE CONVERTOR and spill fluid all over the garage floor once you leave the car parked for any length of time. The fluid backs out right out of the filler tube.

    One way to remedy the problem with the Powerglide is to run the transmission a quart low.......................

    Been there, done that-

    :cool:
     
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  19. 383 240z
    Joined: Oct 28, 2007
    Posts: 429

    383 240z
    Member

    Good luck at the AAMCO. I worked there as an R&R guy early in my career. The joke of the shop, and repeated by ALL the diagnostic guys was " AAMCO stands for All Automatics Must Come Out" Keith
     
  20. park on a level spot and slide a very large piece of cardboard under it marking the floor and cardboard the check it and that will get you close to the leak area. another thing is leaks migrate, i have machinery i work on and to find hyd. leaks i glove up and start checking every surface highest to lowest chasing the leak and sometimes it takes some time but.....
     
  21. I've had the problem on a few Fords, and it always turned out to be a bad seal , usually the Shifter shaft seal.
    Newer Dodge's actually have a converter drain back valve in them, and there are some aftermarket valves available to put in the coolor lines.
     
  22. nutajunka
    Joined: Jan 24, 2007
    Posts: 1,464

    nutajunka

    You should'nt have any leaks unless you have bad o-rings, seals, or gaskets. Just drive it to a car wash and clean it real good if it's all wet and then like meationed place some cardboard under it and watch and wait for your drip to appear. Alot of the dipstick tubes get bent out of shape when doing engine swaps and the o-ring will leak, plus you have to have the bracket that is on the tube bolted, so it can't work loose. I have had to put a new o-ring on the tube with some sealer to stop a few. Keep it simple, start with the basics.
     
    Last edited: May 30, 2012
  23. birdman42
    Joined: Jan 18, 2012
    Posts: 400

    birdman42
    Member

    converter drain back is normal.on a 700r4 the dipstick should ue a boot instead of a o-ring.I have also seen the O-ring around the pump get hard and leak after sitting.
     
  24. olscrounger likes this.
  25. nutajunka
    Joined: Jan 24, 2007
    Posts: 1,464

    nutajunka

  26. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    Haven't dealt with 700 R4s but on most automatic transmissions, the only place fluid should be able to come out is at the vent. Some of the 4 wheel guys I know connect a hose to their vent tubes on axles, transfer casees and transmissions to raise them above any water they drive through. If it is coming out of the vent tube, just add enough hose to make the vent the highest point. There shouldn't be enough fluid in the system to overflow the vent but I suppose it could with a large enough cooler.

    To prevent the cooler oil running back, some simple ball check valves would work. Just make certain you have the flow direction correct.

    Is the vehicle parked on a level surface? I know one guy who parked on his sloped driveway and the trans leaked. I told him to back it in and it solved his problem.
     
  27. d2_willys
    Joined: Sep 8, 2007
    Posts: 4,285

    d2_willys
    Member
    from Kansas

    I agree with the converter drain back valve possibly being defective, but keep the vent open too. If plugged up, the whole box gets pressurized and the fluid will find any weak spot to leak.
     
    olscrounger likes this.
  28. Oldschool Rodder 62
    Joined: May 29, 2018
    Posts: 44

    Oldschool Rodder 62
    Member

    I have a freshly rebuilt 700r4. After it runs a while fluid pukes out the dip stick. I've been told that it is most likely the vent tube being plugged. as luck would have it I can't get to it. Too close to the tunnel. I'm trying to get enough balls to cut the floor to get at it. I'll let you know if that works.
     
  29. jimmy six
    Joined: Mar 21, 2006
    Posts: 14,802

    jimmy six
    ALLIANCE MEMBER

    My converter drains back in a couple of days. The leaks I’ve been fighting are all from it. The level in the dip stick tube will rise 5” on its angle and 4” vertical and even fill part of the tail housing. I just finished adding a tube to the vent up to the top of a rocker cover level I can see. It all sucks back to normal level in less than a minute.

    If you’ve got a bad seal as the trans oil level reaches it the fluid leaks out. If it is the converter you need make sure all the seals are good. Mine didn’t have anything in the threaded hole for the vent. It thru some fluid out on start up causing dripping I could find.. hope I've go it this time. Good luck
     
  30. justpassinthru
    Joined: Jul 23, 2010
    Posts: 524

    justpassinthru
    Member

    It could be that the vent is plugged but it is most likely the trans is overfilled.

    Back in the 80s, GM had that problem in trucks pulling heavy loads. The trans would get hotter than normal and the fluid level would get high enough to get to the rotating parts, then get air in the fluid and expand and go up the tube. Their solution was a factory recall to install a locking dip stick.

    The way to find the proper fluid level, although messy, is to get the trans to operating temp, then with the car level, loosen all the pan bolts and let the excess fluid drain from the trans. Re tighten the bolts, run engine and check level on the dipstick and re-mark the stick. This would be full hot. That would put the fluid level at the pan rail when hot, which is the proper level.
    Then change the pan gasket.

    Bill
     

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