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Tech question "sealing a TH350 tranny pan"

Discussion in 'The Hokey Ass Message Board' started by Roadsir, Jun 18, 2007.

  1. Ok,
    Any tips here? Or are there two types of TH350's......Ones that leak and ones that are going to leak!

    Tranny was rebuilt, but had a used pan. Pan gasket started leaking with original GM pan. I removed the pan, and upon inspection, I could see that it was bent from years of over torqueing and the stamped stiffening ribs in the rail were squashed.

    So I decided to ditch the steel pan. I bought an aluminum pan. I checked this for level on a granite surface plate, hand-filed any die-cast flash, gasket tacked, used a rubber gasket, lightly torqued, and after a spell it started to leak.

    So then I decided a tranny shop must have all the secrets. They installed a cork gasket no sealant, and after a few months it started weeping.

    So...What works best.
    New Steel Pan or Aluminum.
    Rubber gasket?
    Cork gasket?
    "Great Stuff" with or without gasket
    Gasket prep?, Permatex red gasket tack or ??
    Best fastener torque? Loctite blue or Permatex non-hardening on fasteners.

    Seem like it should be a simple deal.....Someone here must have nailed this down.

    Thanks
     
  2. cruisinkruty
    Joined: Jan 22, 2006
    Posts: 314

    cruisinkruty
    Member

    Look at the intermediate accumulator cover O-ring. There is a large spring under the cover,when the spring fails the O-ring will lead right around the pan rail,it will drive ya nuts thinking it is the pan.
     
    VANDENPLAS and bjinatj like this.
  3. I always smeared a THIN coating of clear Silicone on both sides
    of the cork gaskets.Let that set up,then smear a THIN coat on the pan,and apply the gasket.Clothes pins work good for holding the gasket in position while the silicone sets up.

    When that is dry,install as usual,being carefull not to apply too much torque.

    Works great on rocker cover gasket,oil pans,etc.

    Modern "rubber" gaskets should be better than the cheap cork,but I'd still be inclined to glue them on first.

    On out Hart 2 liter,the only gasket was the head gasket.Everything else was silicone.
     
  4. Gasgasinch always worked well,smells like Contact Cement,only costs more.

    Coating the cheap gaskets makes them live longer.
    First choice is better gaskets.
     
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  5. cruisinkruty....I am pretty sure this is dry, but I'll double check. I did check the dipstick tube (New Miloden braided version) and the kickdown (lokar) and the seal around the shifter shaft....All are dry. Also checked the front seal to make sure it was dry

     
  6. cruisinkruty
    Joined: Jan 22, 2006
    Posts: 314

    cruisinkruty
    Member

    Very carefully spray the area clean with starting fluid or brakekleen.It will wash all oily residue away and leave a dry clean area,Drive vehicle and check for leaks..
     
  7. Dooley
    Joined: May 29, 2002
    Posts: 2,535

    Dooley
    Member
    from Buffalo NY

    I had a leak on my powerglide that I could not figure out.
    Check to make sure none of the bolt holes are stipped, that was my problem, also I used a stock pan and spent some time with a straight edge and a body hammer, once I did that and fixed the stripped bolt, I used a cork gasket dry and no leaks.
     
  8. 40 & 61 Fords
    Joined: May 17, 2006
    Posts: 2,000

    40 & 61 Fords
    Member

    I run into this same problem with my TH350. I've been through 3 types of pans, and 3 types of dipsticks and still had leaks. Maybe I'm replaceing the wrong parts. :)
     

  9. If you clean it off,let dry,then spray in gray primer,
    the leaks are easier to see.If it doesn't leak at idle,
    drive around the block once.Should be obvious.

    Works great on leaky oil pans.I've found the holes
    rusted through the side of 3 oil pans that way.
     
  10. MEDDLER1
    Joined: Jun 1, 2006
    Posts: 1,593

    MEDDLER1
    Member

    i always install the pans dry with very little torque to the bolts after i drive it for about 20 minutes i re tighten them barely after it cools.its always been 50/50 for me.any glues or sealers just cause problems contaminating the internals and its just a bitch to get off when your lying on the floor under your ride.
     
  11. Thanks for the advice, everyone. I plan on ripping into this tomorrow night...Any other suggestions would be appreciated.

    Eric
     
  12. 348tripower
    Joined: Sep 19, 2004
    Posts: 328

    348tripower
    Member

    Have a look at the dipstick and the TV cable. I was chasing oil leaks in two transmissions. A 700r4 which ended up being both of the above and a 350 with a cheap aftermarket tv cable. It leaked too. The cable on the 350 just slip into the mount, letting oil leak out under pressure. Both of these transmissions led me to beleive it was the pan that was leaking!
    Don
     
  13. Fairlane Dave
    Joined: Mar 23, 2007
    Posts: 634

    Fairlane Dave
    Member

    If it is the pan, go to a Toyota parts counter and ask for their orange transmission pan sealer. It is GREAT stuff! Toyota techs (and the factory) use it and it has all but eliminated tranny pan leaks for Toyota. Some new Toyota cars have it as the pan gasket straight from the assembly plant. It's expensive (about $20 a tube), but I can testify that it works great. I had a very stubborn tranny pan leak on my Fairlane and tried everything with no luck. Someone on the Ford Six message board recommended it and it worked perfectly the first time. One tube is enough to seal two pans. Just like any other sealer, make sure none if it runs into the pan. It doesn't take much of this stuff to seal it.
     
  14. squirrel
    Joined: Sep 23, 2004
    Posts: 42,705

    squirrel
    Member

    Usually the pans are not bad enough to get rid of, but they do need the bolt holes tapped back down. And you should not need to use any sealer on the pan gasket.

    Typical places that leak on a th350:

    Shift shaft seal
    Dipstick tube O ring, the tube gets bent up or it's junk chinese chrome.
    Speedometer seal, either the seal or gear or both can wear out
    Speedometer sleeve, pot metal ones wear out
    Kickdown cable or O ring. The cable housing itself can leak.
    Acuumulator O ring
    Lockup wiring connector if it's a TH350C or TH250C
    TCS switch, like an oil pressure sender, usually not needed, plug the hole
     
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  15. Mr.Musico
    Joined: Jan 7, 2007
    Posts: 1,575

    Mr.Musico
    Member
    from SoCal

    the orginal pan usually is better than any aftermarket crap. usually need to straighten the pan and "flatten" out the raised areas around the bolt holes- raised bacuse most people over tighten the pan.
     
  16. Ichoptop
    Joined: Mar 5, 2001
    Posts: 721

    Ichoptop
    Member

    light coating of blue permatex on both sides of the gasket, wait 5 mintues and install on cleaned surfaces. Do not torque. Let gasket maker cure for a few hours, torque to spec. Been working for me for 10 years.
     
    Baumi likes this.
  17. 40Standard
    Joined: Jul 30, 2005
    Posts: 5,725

    40Standard
    Member
    from Indy

    use a dry cork gasket and hammer the bolt holes flat in the pan. overtightening causes the bolt holes to form a ridge
     
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  18. I ended using Red permatex on both sides of the rubber gasket. I evened it out with an acid brush. Both surfaces were prepped with Acetone. I installed it with all fasteners snug. Came back an hour later and gave them all a 1/4 to 1/2 turn.

    No Leaks! after 250 miles..

    Thanks for the advice
     
    Baumi likes this.
  19. UnIOnViLLEHauNT
    Joined: Jun 22, 2004
    Posts: 4,814

    UnIOnViLLEHauNT
    Member

    I too get down with the hammer tapping of the bolt holes. Works well.
     
    Baumi likes this.
  20. WoodWardWilly
    Joined: Mar 13, 2010
    Posts: 13

    WoodWardWilly
    Member

    Try Indian Head Gasket Shellac by Permatex. Comes in a little brown bottle and the lid has a swab. $2.99 at most auto stores. Give the pan, gasket and tranny a thin coat and let dry completely and then assembly. Don't over tighten the bolts. Also.. I use a drop of blue loctite on the bolts as they tend to loosen from vibration. Just remember to clean all the oil from the bolts and tranny before using the loctite or it won't work. Been doing this technique for years and years and no leaks from the gasket. Check the tranny areas above the pan that can leak and run down to the pan and make it look like a bad gasket. You can dust the tranny with baby powder to find the leaks easier.
     
    olscrounger likes this.
  21. I figured out how the get rid of the leak.. I sold the car! Seriously I ended up going to an OEM pan, Serrated washer head fasteners, bought a new torque wrench, tried a cork gasket. Guess what....


    Still leaked.

    I am wondering if the rake, and fill level played a roll. It was an aftermarket dipstick...maybe it was off a little and fill was too high??
     
  22. Old thread and I bet the damn thing is still leaking.
    I’ve got an idea, I’ll let you know how it works out.
     
  23. Mr48chev
    Joined: Dec 28, 2007
    Posts: 25,004

    Mr48chev
    ALLIANCE MEMBER

    I walked into a long time friend of mines transmission shop a couple of years ago to get a speedometer gear to correct my speedometer and noticed that he had cork pan gaskets hanging on the wall. Asked his wife who is also the parts gal/office manager and she said that what he used. Bought one and put it on mine and no more leaks so far. I've never seen a Turbo 350 pan that didn't need the areas around the bolt holes flattened out. The transmission man I worked next to in Texas in the 70's had a piece of flat bar he chucked in the vise that was the right width to fit in between the side of the pan and the rolled over lip that he used as an anvil. He had flattening those things out down to a science.
     
  24. squirrel
    Joined: Sep 23, 2004
    Posts: 42,705

    squirrel
    Member

    when I worked at the transmission shop 35+ years ago, we always used cork gaskets, and we always wire brushed and flattened the gasket surface on the pan. Every one.
     
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  25. Dan Timberlake
    Joined: Apr 28, 2010
    Posts: 1,233

    Dan Timberlake
    Member

    I really like a very thin smear of Ultra Gray as a gasket "dressing."
    For one thing The color blends in nicely, unlike red and blue, which kind of scream "hack job," even when not oozing out to form a 3/16" bead at the sealed joint.
    It is very firm bodied too, intended to be a formed in place gasket.

    Apologies to those who use the red and blue RTV, which really are excellent products.
     
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  26. rockable
    Joined: Dec 21, 2009
    Posts: 2,570

    rockable
    ALLIANCE MEMBER

    In my experien experience, the rubber gaskets always leak. I wont use them. Use the cork composite type and make sure both surfaces are flat.
     
  27. bonneville bones
    Joined: May 17, 2006
    Posts: 103

    bonneville bones
    Member

    Aftermarket aluminum pan seals real nice!


    Sent from my iPhone using H.A.M.B.
     
  28. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 1,759

    OLDSMAN
    Member

    I built transmissions for over 40 years professionally, I never used sealer of any kind on pan gaskets. On 350 TH transmissions tap the bolt holes flat again. As been said OEM pans are better than aftermarket pans
     
  29. Haha, this is an old thread...Maybe I should start a new one....How do I keep garage floor epoxy sticking to spot where my Turbo 350 leaked 9 years ago...

    My latest cure is two out my three cars have manuals....they don't leave a drop!

     
  30. VANDENPLAS
    Joined: Dec 14, 2009
    Posts: 1,720

    VANDENPLAS
    Member

    stock steel pan

    Flatten the bolt holes down from over tightening

    Cork gasket dry no other sealers needed

    Use a speed handle and just your open palm to tighten

    Might need to retorque later.

    Most tranny shops still use cork for pan gaskets and it’s not because they are cheaper but because they work.

    And a quick way to fix stripped pan bolts is to use a small thin cotter pin
    Open it up and stick one side in the hole along with the bolt.
    It will tighten down fine and hold torque
    And trim off the end hanging out.

    Quick cheep “Heli coil” into aluminum. Would not use it in a critical area but works great for pan bolts.
     

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