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How to fix a leaky trans pan?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BayouBlazer88, Oct 6, 2003.

  1. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    I can't seem to find a way to stop this thing from leaking. I never had a problem with it leaking before until I changed my transmission fluid for the first time (it needed it badly). I bought a new filter from Autozone which comes with a cork seal (which worked about as well as a screen door on a battle ship). I didn't have a torque wrench that read in inch-pounds at the time so I just torqued it to the lowest my wrench would go which was 20ft-lb, so I may have warped the pan in the process. So about a month ago I put one of those good rubber pan seals from O'reilly on it (Autozone doesn't sell them) thinking it would definitely solve the problem, but a week later it started leaking again. I was thinking about just using a thick bead of silicone around the pan instead of a seal. Would that work? I've heard the ATF will eat up silcone, is this true? Any other suggestions? Thanks.
     
  2. Confedneck

    Confedneck 3/4 ton status

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    use the oil/gas proof silicone sealer thin between the pan and gasket, when it sets up tacky, install the pan and gasket together..
     
  3. 77Jimmy

    77Jimmy 1/2 ton status

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    Good timing on your post...I'm having the same problem. I bought a new stock pan, put in a drain plug/temp sensor and used a Fel-Pro gasket and the thing is still leaking. /forums/images/graemlins/angryfire.gif I think the pan was warped from day one so that's what I believe is now causing my leak...I've eliminated every other possibility. I've seen some other posts on here not to use any kind of RTV.

    I'm thinking of buying a chrome pan (not for bling bling reason, b/c it's steel) or *maybe* a cast aluminum pan that I know will be dead flat/level.
     
  4. justhorsinaround

    justhorsinaround 3/4 ton status

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    hehe I hate to be picky but "it's a screen door on a submarine." /forums/images/graemlins/tongue.gif Be that as it may though, I agree with Confedneck, put some silicone on your existing gasket and then tighten it down in a crosshatch pattern. If that doesn't work then start throwin money at it for new pans. Good luck to ya.

    Allan
     
  5. POWERMAD

    POWERMAD 1/2 ton status

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    Yep just squirt a bead around the mating surface and when the filter picks up all the material that squeezed out and starts to cavitate... or gets stuck in a vital part...
    It sounds like you warped the flange. Once it is down see how bad it is, usualy you can use a small hammer and straighten it. If in doubt get another pan they are pretty cheap. use a rubber gasget they are more forgiving than the cork ones, if you don't have an inch pound wrench just use a 1/4" drive rachet. make sure that all the bolts are a flange head or use a flatwasher under a regular bolt.
    I use <font color="green">green </font> locktite on them for peice of mind.
     
  6. Lance

    Lance 1/2 ton status

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    i've posted this before, but try re-torquing them w/ 1/4" drive ratchet after you get the tranny hot. do not let it cool back down. the principle is that the metal gets hot and expands, then it cools and contracts creating a leak around the pan. using the 1/4" drive will prevent you from over-tightening and eventually stripping the bolts. only use one hand when tightening them up. this worked for me and stopped my pan leak. good luck.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    First off, don't trust 100+ ft lb torque wrenches below about 20 ft lbs. BTDT, it wasn't accurate in the slightest.

    Pull the pan back off, check the pan rails for straightness. The problem area with overtorqued bolts will be the holes where the bolts pass through. Take a hammer and flatten them back out. Usually you can put the pan edge on the side of a table, and tap them out.

    As to the silicone on the pan being a bad idea, I'm sick of reading that. You put silicone on the intake gasket of a SBC, the valve covers, you put it on a diff cover, and people are worried about putting it on a transmission with an effective filter?

    I've used it on every auto tranny I've put together (because the neoprene or rubber gaskets work well with it) and unless you get crazy with the stuff, it won't hurt a damn thing. The problem is the same as what happens on engines. Someone gets crazy with the tube, and ends up sucking silicone into the pump pickup, which restricts flow. (potentially) If you wanna use silicone, make sure you use an extremely thin bead (spread it with your finger so it's thin enough to see through in places), and be happy. Just don't tell me it's always bad, because it hasn't caused a single problem in the (likely) hundreds of tims I've pulled my tranny pans)

    But if you don't get the flange flat, it will never seal no matter how much silicone you use.
     
  8. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I've heard to use Vaseline on both sides of the gasket to seal up leaks. /forums/images/graemlins/thinking.gif
     
  9. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Maybe the pan isn't leaking at all.

    Front pump housing seal goes it runs down the front of the housing and come out right at the front lip of the pan. On TH350's the 1-2 shift acumulator is prone to leaking and it runs right down onto the passengerside of the pan and depending how it's parked leaks right on the front driveshaft. O-ring on the dipstick caused the same sort of leak.
     
  10. BayouBlazer88

    BayouBlazer88 1/2 ton status

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    Well first of all, I have a 700R4 so I'm not sure if the 1-2 shift accumulator is prone to leaking on these too. Also, I put in a brand new dipstick seal so I doubt it's leaking from there. However, it is leaking from the exact spot that you said, passenger side and front side. It doesn't really leak from the back or driver side. This weekend I'll put some black RTV sealant on both sides of the rubber gasket and torque up the pan and hope it works. I may even try petroleum jelly. Also, where can you buy new transmission pans for a 700R4?
     
  11. POWERMAD

    POWERMAD 1/2 ton status

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    If you want to assemble stuff with silicone have at it.
    The only thing I use on gasgets is high tac. Use the spray type and it is good for .010" .
    Using silicone on a diff cover or a drop in is is quite a bit different than using it on an engine or tranny.
    If you have to use silicone to seal a pan or valve cover it it time to either fix it or get a new one.
    From doing hundreds of tranny sevices and repairs I don't ever recall a tube of silicone and a note in the box saying if you have a leak spread this around and yer good to go.
    Maby I'm anal but unless that is what it takes to get me home I don't use it.
    For cork gasgets I use High Tac on the pan side and smear grease on the other side.
    I dunno when you fix rigs for a paycheck you tend to eleiminate all possibilities for a come back.
    I get paid by the hr but a come back can wipe out my effiecency bonus for the month.
    I didn't want to spring for a new set of valve covers for my 73. So I smeared a thin layer of silicone on the Fel-pro rubber gasgets and walla.. no more leak.
    I am stop at a light and it looks like I have an engine fire.
    I pop the hood at the next service station and oil is spewing out the vent and all over the header.
    I peel the cover off and find a bit of silicone covering the drain back hole.
    I have a new set of covers and spreaders ready to install now. Painted fresh Chevy orange.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    If you can afford to replace whatever bent pieces you have, good for you. Some people can't, and I don't know where you are from, but a tranny pan is a lot more expensive than a tube of silicone.

    Don't see how using silicone on a valve cover gasket is any different than using it for the front and rear of the intake, or the corners of the oil pan gasket(s) which, it is my understanding, is recommended by just about every engine builder in the country.
     
  13. imiceman44

    imiceman44 1 ton status

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    To add my voice to the list of opinions here:
    First don't even check I know the bolt holes are pushed in if you torqued it too much flatten these out with a small hammer, I usualy put a small hammer on the vise and then use it as a support for the pan rail and pound on it from the other side.
    Second any gasket will do wether neprene, rubber or cork as long as you don't over torque it, and the 1/4" ratchet is your friend here. One handed and if you are a body builder 2 fingered. /forums/images/graemlins/rotfl.gif
    Third, if you want to use any help, petrolueum gelly is good for rubber and neoprene because it will let it stick so it doesn't fall off and in the same time will not let it get pinched and kink for a leak, it will slip flat and seal better.
    For the cork type gasket I use either Hi tac or silicone and like Dorian said, spread with your finger just enough to be like glue not filler, it will help hold it in place, not seal better.
    Fourth and that is also important as someone mentionned, torque in criss cross not sequential.
    Good luck, it took me 3 tries to learn how to seal it good now it's always good. /forums/images/graemlins/thumb.gif
     
  14. POWERMAD

    POWERMAD 1/2 ton status

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    Umm we are talkin about tin.. not a bling aluminumn peice.
    Not exactly a high $$ item.
    Ya that $15 for new covers was a bit more than a tube of silicone..
    But WTF my covers don't spew oil all over my headers anymore.
    Unless the tin is 30 years old and has just been beat to crap it can be straightened eaisily will require nothing more than the supplied gasget.
    If I am far from home and that is all I have to make it to home port then yep I will break it out.
    Even still I have gasget material and a 2oz ball peen hammer.
    Peace dude.... I had no idea tin valve covers and such was so exspensive up there.
    Using silicone to stop a leak is nothing more than a bandaid.
    I hope I didn't step on yer mechanical toes.
    Everyone has their own way of doing things... I don't use silicone, you use it... great, kickass, all righty then.
    I don't, I'll wake up the same as you and we will still do things our own way.
    Peace bro.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    [ QUOTE ]
    Umm we are talkin about tin.. not a bling aluminumn peice.


    [/ QUOTE ]

    So you can get $15 tranny pans from GM eh?
     
  16. POWERMAD

    POWERMAD 1/2 ton status

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    I think I dropped $40 on a pan for my 73's Th400, that one holds 2 more qts than a stock one.
    I installed that one just for the extra capicity.
    I can't imagine that a stock pan is much more than that.
    I belive a B&amp;M stamped steel pan with the extra 2 qts with cooling fins on the bottom is only $45 or so for a 700r4 tranny.
    Stock pans and such can usualy be found for dirt cheap.
    I am willing to take a bet that you can find a shload of stock 700r4's that are junk and get the pan for $10 (or free)
    Provided the one you are using is not so whacked that it cannot be straightened. /forums/images/graemlins/grin.gif
    And tranny pans do not see as much on and off action as say a valve cover. Unless ya install it with an impact and stretch the metal so bad that the only thing it is good for is target practice. /forums/images/graemlins/laugh.gif
     

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