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700r4 Problem on a 86 Blazer

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mrjay, Dec 19, 2002.

  1. mrjay

    mrjay Registered Member

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    When the torque converter locks up the truck starts to shutter. This happens between 40 and 50 mph. Once I get over 50, the shutter starts to let up. The vacuum switch is not connected. Is the TC going bad or is it a tranny problem or what?

    Thanks for the help!
    Jay.

    I had a Ford once, then I grew up.
     
  2. azblazor

    azblazor 1/2 ton status Premium Member

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    Why is the vacuum switch disconnected? I am not a 700r4 expert but I have had them rebuilt. I would ask around and find a GOOD trany shop that will look at it. It sounds like to me that the TC is going.
     
  3. 95 Silverado

    95 Silverado 1/2 ton status

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    does it shutter when it shifts into fourth gear? or when the convertor locks up? if the vacuum switch isn't hooked up the convertor is probably not locking up, unless the wiring has been changed to bypass the vacuum switch. It could be slipping when it shifts into fourth gear. As the previous post suggested, better get it checked out before it goes out completely.
     
  4. Pure Insanity

    Pure Insanity 1/2 ton status

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    If you have the switch disconnected its not getting the correct signals to operate properly.

    Ill agree w/ the other 2 posts, get it checked out fastlike. Once a 700 starts acting up, it doesnst take long to toast them.
     
  5. mrjay

    mrjay Registered Member

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    I think you'all are on the right track. As I understand it, the 700r4 shifts and locks up based on two inputs; the pressure from the hydraulic pump (based on input rpm) and the electric signal from the vacuum switch. I was told that the tranny would operate just fine only on the hydraulic pressure. I'm thinking that without the electric input, the torque converter is trying to lockup too early and doesn't have enough hydraulic pressure to maintain the lockup at the lower rpm.
    I think I'm going to explore this some more.

    Thanks Jay.
     
  6. Muley

    Muley 1/2 ton status

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    </font><blockquote><font class="small">In reply to:</font><hr />
    I'm thinking that without the electric input, the torque converter is trying to lockup too early and doesn't have enough hydraulic pressure to maintain the lockup at the lower rpm.


    [/ QUOTE ]

    hook it back up then before you roast the TC.
     
  7. milspecjimmy

    milspecjimmy 1/2 ton status

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    mine started doing this about 2 months ago, i changed the fluid and all was good, until......... it started slipping when it was cold. i ended up needing every internal part except the main shaft. like the pump, drum, and all the mechainical parts. luckly i have a friend who owns a tranny shop and did it for $100 he told me it should have run into 13-1400 dollar range. id go get it checked. this is the 2nd 700 ive roasted and the 10th tranny ( 7 4L60e's, a 727tf and 2 700's) 2 died from drowning, 1 from heat, and 7 in one summer from too much horse power and way too many drag race nights at NED in the ole 94 Z-28. any way get it checked ASAP and get it fixxed before the ole $$$$$ starts piling up.
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  8. Sandman

    Sandman 3/4 ton status Author

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    Wow, I think you could buy one for less than that! /forums/images/graemlins/eek.gif
     
  9. milspecjimmy

    milspecjimmy 1/2 ton status

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    yeah you could, like i said he was a friend, and had a lot of parts laying around. any time you get into replacing a lot of parts in one thing you can easily exceed the cost of replacing the item rather than continue the rebuild.
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     

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