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700R4 trans leak

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by badfish4tail, Apr 13, 2005.

  1. badfish4tail

    badfish4tail 1/2 ton status

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    My front oil pump seal is leaking on my 91 K5 700r4 transmission. At least i think that is were it is leaking from. I thought it was from the pan, but i already resealed the pan and the trans still leaks at freeway speeds from just under the bell housing. I talked to a tech friend of mine and he said it is coming from the front pump seal. He says i should change the seal and o-ring and told me that it is a big job. So my question is should i spend the money and replace it, or should i start lookin for another trans?
    This trans has given me no problems other than this leak........
     
  2. 6.2 man

    6.2 man 1/2 ton status

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    Thats what happened to mine a while back . I took it to a transmission shop and they pulled it and found the pump was going and I replaced it and the converter. Seems never as easy as replacing a seal ? Yours maybe different ?
     
  3. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    if the seal is leaking, ill put money on the bushing behind it is bad also. that requires a pump removal to change it, unless you have a $400 tool to remove and install the bushing with the pump in the trans.
     
  4. trailblazer86

    trailblazer86 1/2 ton status

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    Did you check the O ring at the dipstick tube?
    That is were mine is leaking right now. After I drive it there is a few drops on the inspection cover but it is dry inside in front of and behind the converter.
    My leak is just a few drops now and then. No puddles under the truck.
     
  5. badfish4tail

    badfish4tail 1/2 ton status

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    I just took another look at my leak area and noticed that the starter has fluid drip's from it. Would this more piont to the dip stick?
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Are you running the inspection plate/dust shield for the trans?

    The converter will sling fluid all over the place if it's getting oil on it, so if you aren't running an inspection cover, that might be why you see it elsewhere.

    Pretty common "problem" on the 700's, not sure when they fixed the issue, but that front seal and I think even the bushing by design tend to get forced out of their bore by fluid pressure building up behind them.
     
  7. trailblazer86

    trailblazer86 1/2 ton status

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    Sorry about that. I was talking about the transmission dip stick tube.
     
  8. hd-10

    hd-10 1/2 ton status

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    well ifigure i will through this out there cause it happened to me but the breather hose from your transfer case might be on top of your tranny and fluid is leaking done from that i now it sounds stupid but it did happen to me and i could find out were the hell i was leaking from untill i glanced at that hose and saw tranny fluid coming out. just a thought
     
  9. 84k5

    84k5 1/2 ton status

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    For what it is worth...I just had the same problem. Front pump seal was leaking; I took it to the dealership to get fixed as I don't have the time or tools to fix it. ~50 miles after this the transmission went completely out and left me stranded far from home. They offered to refund all the money if I get the new transmission from them...I really don't want to put another 700r4 in it. It only lasted 118xxx with a fricken 305 in front of it.
     
  10. badfish4tail

    badfish4tail 1/2 ton status

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    Well thanks for all the advise, but I will have to put the trans on the back burner due to my fuel pump going out :doah:
     
  11. trailblazer86

    trailblazer86 1/2 ton status

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    www.transmissioncenter.net/700r4.htm

    If you want Information about the 700 R4 Check out this site.
    They can build you a 700 that will take more abuse than most can dish out.
    One transmission (TH700) can tow in fourth gear behind a big block.
    Then they will deliver it to your door for free.

    Read through the whole site. The information is more than worth your time.

    About the front seal blowing out they say, (Paraphrased) The problem must be fixed or the seal will just blow out again.
     

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