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Leaking ATF from Rear of Tranny, please help!

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by dawson444, Apr 11, 2002.

  1. dawson444

    dawson444 1/2 ton status

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    My truck is leaking ATF from the rear of the tranny. What could be causing this? I really can't tell where is is coming from, it is collecting on the t case cross memeber and then dripping. What can I check?
    Please help, do I need to pull the t case and put more sealant around where tranny meets adapter or what?
    Thanks!
    BTW- it is a TH400/203
     
  2. wayne

    wayne 3/4 ton status

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    By the sounds of it Dawson you are going to have to pull it apart. Put a new output seal in the trans.
     
  3. 76_Cheyenne

    76_Cheyenne 1/2 ton status

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    Get some degreaser and clean up the area all around and dry it off. Watch for the leak and fix the seal where the leak comes from. I sounds like a tranny pan. If it is get a filter/gasket kit at schucks or Napa, and about 5liters of Dexron ATF fluid for a TH350. Drop the pan, front bolts first, let it drain then the whole pan. Replace the filter. clean the pan and tranny where the pan bolts up. Put on the new gasket, don't use silicon sealer!!! only the gasket is needed. You can put a little grease on the pan to hold the gasket in place. Then start adding fluid but make sure you don't overfill it. once you get about 4 liters in run the engine and get the truck to normal operating temp. be on flat ground then check and add fluid as nessesary. Hope that helps.
     
  4. dawson444

    dawson444 1/2 ton status

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  5. weisel

    weisel 1/2 ton status

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    Like he said. Before tearing into it, find out what it is comming from by cleaning it all off first then seeing where it leaks out. I am not sure about the th400, but my th350/203 did not have a output shaft seal on the tranny. Just had a gasket between the two parts.
     
  6. txguy

    txguy 1/2 ton status

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    Make that 2. I am having the same problem. Is it more than likely the transmission pan, or could it be the transfer case to transmission bolt up points? Mine seems to be intermittant. Maybe heat related.

    Thanks
     
  7. efilnikufecin

    efilnikufecin 1/2 ton status

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    i had a leak same as yours.i was coming out between the tranny and the adapter.i made a new gasket from gasket material and used a bunch of high tack to make sure it did not leak again.pulling a 203 in and out sucks but thats what i had to do to get it to stop leaking.
     
  8. GMCLegacy

    GMCLegacy 1/2 ton status

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    inspect your tranny to t-case adapter also for hairline cracks. i broke my 350/205 adapter, it was cracked on the top of the adapter, it made it look like it was the seal between the tranny and tcase.
     

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