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th400 pan wont stop leaking.

Discussion in 'The Garage' started by desertrat67, Dec 12, 2004.

  1. desertrat67

    desertrat67 Hawk Driver

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    I have tried paper gaskets, cork gaskets, blue RTV, red RTV, black RTV, what the hell am i doing wrong? The pan itself has been changed as well. I am tired of having to replace the gasket every couple of months because it starts leaking again.
     
  2. diesel4me

    diesel4me 1 ton status Premium Member

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    You might be overtightening the bolts and bending the pan where the bolts go thru--I have to hammer many tranny pans flat before changing the gasket(same with valve covers too),I got an aluminum pan for my TH400 a freind gave me-he was disgusted with it constantly dripping no matter what he did--I didnt put it on yet--but I noticed the gasket still glued on it had slipped inside in one spot,and it was a cheap rubber/cork gasket--I'm willing to bet when I put it on mine with a WIX gasket and filter,with a small amount of 3M weatherstrip adhesive it wont leak a drop...I dont like using RTV on a tranny,its too easy for some to get into the tranny and plug something up......hope this helps....good luck..Hate to suggest this,but have you looked carefully for any hairline cracks in the case where the pan bolts up--a few "leakers" I had were cracked from somebody putting a metric bolt in an american bolt hole.....hope thats not the case....
     
  3. MOABDADC22

    MOABDADC22 1/2 ton status

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    Yeah, too many people tighten these down way too tight. You should never have to use any sealant on an AT gasket.
     
  4. tarussell

    tarussell 1/2 ton status

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    Another vote for over tight pan bolts.

    Tom
     
  5. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    the pan bolts only take 11-12 ft lbs of torque.
     
  6. y5mgisi

    y5mgisi 1 ton status

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    You absulutly sure its the pan and its not driping down like from the cooler lines?
     
  7. kick

    kick 1/2 ton status

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    It's possible that the pan maybe warped by over torquing bolts. Get a new pan and if you have no torque wrench just snug up the bolts. fight the urge to over tighten and compesss the gasket. I've used the stock pan gaskets for years and still use the stock gasket on my aftermarket pan which has cooling fins and allows for 2-3 qts. more tranny fluid. I had to wrap the bolts with teflon tape to prevent fluid seeping thru the threads.
     
  8. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Good point, I thought my pan was leaking at one point; and it was actually where the dipstick tube entered the tranny. The rubber seal thingy wasn't seated properly.
     
  9. 3 on the tree

    3 on the tree 1/2 ton status

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    I had a 727 that was a chronic leaker. I used a small hammer and 1X4 on edge to tap all the bolt holes flat again. Then I got a handful of those old Chevy washers(?) that go under the valve cover bolts and used them where there was clearance. Finally solved my leak. Try putting a good straightedge over your pan flange and look for high spots that will keep the gasket from sealing properly,then flatten the high spots out of the flange.
     
  10. sublmnl1990

    sublmnl1990 1/2 ton status

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    On my first burb I decided to change my trans fluid my self got one of those fancy deep pans, 1st mistake was I was using rv sealer and the gasket, then I was over tightening them, went to dealer got cork gasket just snugged them up and never had a drip again. Now I feel old cause that was like 25 years ago. :cool1:
     
  11. blazen86

    blazen86 Registered Member

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    If its the tranny, try the BG stuff that comes in the Can, ill get the exact name tommorow, its at the shop, but i put that in mine b/c the front seal was leaking and its been about three weeks and the gravel in the driveway is starting to dry up so it must be working.
     
  12. desertrat67

    desertrat67 Hawk Driver

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    I have hammered the pan flat once, and i don't put that much torque on the bolts, but maybe i'll try it with a torque wrench and new gasket and use the recommended tightening sequence. Thanks all for the replies.

    ryan
     
  13. blazen86

    blazen86 Registered Member

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    Well if that doesnt work or anybody gets a leak in a seal, this stuff works awsome, takes a month or so but it works.
    BG Automatic Transmission Fluid
    ATC+ conditioner
     

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