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Probably a way dumb question but, for the Tranny Experts out there...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rem7600, Jul 28, 2002.

  1. rem7600

    rem7600 1/2 ton status

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    To change or not to change, that is the question...

    If I do, I will have a full "flush" done of the system.

    89 GMC K5 4X4, 700 in it. It has 158K on it and never
    been rebuilt. I'm hesitant to change anything that
    works at this age. If I change it what are the chances
    the fresh tranny fluid is going to frig something up?
    It shifts fine now and I have no reason to change
    other than preventative maintenance.

    Answers please! Speak up and be heard! /forums/images/icons/smile.gif
     
  2. rem7600

    rem7600 1/2 ton status

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    No One?
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    How dirty is the fluid? If it needs to be changed and you leave it in, you're going to fry it anyhow.

    I see what you're worried about, but by 89 virtually all the bugs were worked out of the 700. I would go ahead and change the fluid if you feel it's time.
     
  4. Thunder

    Thunder 3/4 ton status

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    Change it. Running old fluid in a 700 will only cause wear. I change the fluid in mine at least once a year. Or about every 8 to 10 K miles.
    There is no way changing the fluid can harm the trans.
    Changing the fluid may make a mechanical problem more noticible.But If it does, the trans was on the way out anyhow.
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Thunder said what I was trying to say, only he did it better. /forums/images/icons/blush.gif
     
  6. rem7600

    rem7600 1/2 ton status

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    Thanks guys...

    It's time for a change regardless of how it LOOKS! /forums/images/icons/shocked.gif
     
  7. tipoil

    tipoil 1/2 ton status

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    And if u want a little firmer shift put "type-f" in
    should helped whit the cluth wear a bit or put a shift kit in it . (the way i would go!!)be sure to flush the torque and the cooler too . (u only change about half the fluid if u only do the pan)

    One thing to remember :
    soft shift=more clutch wear=a other dead 700!!!!
     
  8. Blue85

    Blue85 Troll Premium Member

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    No, sometimes changing the fluid can harm the trans. New ATF is a detergent. If you have a lot of crud built up on stuff, the new fluid can break it up so it can get stuck in a valve or something. If it was me, I would still change it, unless I was planning to sell it soon. It will have to be done eventually, anyway. The sooner the better. Some people recommend that if it hasn't been changed for a long time, to change it again not too long after the first change, to get rid of any crud that the new fluid broke loose.
     
  9. Thunder

    Thunder 3/4 ton status

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    I forgot to add to my first post that you should drop the pan clean it out and change the filter before doing the flush.
    I still say changing the fluid cant hurt it. Old fluid is bad for trannys. When it starts to deteriate corrosives start to form in it that weaken and sometimes harden the seals and other soft parts in the trans. Old fluid has lost its lubricating qualities and does not have the proper fricition properties that the clutches need.
    If a tranny is so dirty that changing the fluid is going to break up some "crud" and stick a valve or cause it to slip. That trans is not long for this world anyhow. Trannys should be clean inside. A dirty tranny is a dead or dieing tranny.
    A very fine grey or black deposit in the bottom of the pan is normal for a high milage tranny. But chunks of stuff or pieces of metal are a sign that the tranny is wearing out.
     

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