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700r4 lockup questions

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Cavalry, Mar 3, 2001.

  1. Cavalry

    Cavalry 1/2 ton status

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    I have a 700r4 in my rig. When I swapped in my new engine for some reason I neglected to hook up the temperature control for the torque converter (vac line) Its just been pulling vac all the time with no switch. The trans still runs strong. I can assume most of the switchs function is driveability in the cold, but could I have screwed anything up?

    Luke
    84 K5
    [​IMG]
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    Your converter probably was never locking then. If anything, since it is still working, at worst, you accelerated wear from the added heat. Check the fluid for color/smell. If it needs replacing, replace it. (the fluid that is)

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A><P ID="edit"><FONT SIZE=-1>Edited by dyeager535 on 03/05/01 11:21 PM (server time).</FONT></P>
     
  3. Blue85

    Blue85 Troll Premium Member

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    What switch wasn't hooked up? Sometimes there are two: one that tells the tranny that there is sufficient vacuum to lock-up and another that switches vacuum flow when the converter is locked (to change timing, maybe?). If the first one was disconnected, you weren't locking up

    <font color=blue>"Who are these guys?" --Al Gore, referring to busts of Jefferson, Washington and Franklin on a televised tour of Monticello.</font color=blue>
     
  4. Emmettology 101

    Emmettology 101 3/4 ton status

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    I would get it checked out. If it is not allowing the converter to lock up then you may be harming the tranny.
    When my bro put in his 700r4 he didn't hook up the 4 wire harness because he doesn't have a comp. A few tranny shops said that as long as he didn't use OD he would be fine. But htey said if he used OD, the convertor wouldn't lkock up and it would burn up 4th.

    I would get it checked out.

    Mike [​IMG]
    See <font color=green>EMMETT</font color=green> -&gt; <A target="_blank" HREF=http://emmett.coloradok5.com>http://emmett.coloradok5.com</A>
     
  5. Cavalry

    Cavalry 1/2 ton status

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    I remember checking the vac temp switch when I did the new engine. At operating temp the trans is receiving vac. So I would assume this is a switch to prevent lockup before the engine is warmed up. If this is true all I would be doing is allowing the trans to lockup before it is warm. I use this truck daily, have no shift problems, burnt fluid, etc So I doubt that I have injured the trans, I just want to know how much excessive wear I put on it.

    Luke
    84 K5
    [​IMG]
     
  6. Blue85b

    Blue85b Registered Member

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    Any excessive wear will be on the torque converter alone. The fluid from the converter is common with all the other tranny fluid and is cooled by the same cooler. If you have been driving in cold weather the whole time, or if you have a big auxillary cooler, the danger will not have been that bad. If you had been towing through death valley with the stock cooler, it would be dead already. If you don't want to run lock-up, you should replace your torque converter with a non-lock-up type.

    As for the 700R4 wiring:
    If you ever leave the four wire connector off of the transmission, the converter will NEVER lock in any gear (it's electric after all...). With just one wire connected it will lock only in high gear. With the whole thing connected it will lock in 2nd, 3rd and 4th, depending on engine load.
     
  7. River

    River 1/2 ton status

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    TH700R4 is not electronic everything is hydraulic only some things are controlled by electric switches. But in o.d. it will lock up (hydraulic) whit or whitout the 4 wires connected.

    But i don`t understand the vacuum line your all talking about, i never have seen a TH700R4 whit a vacuum line connected at the transmission.

    Greetings from Amsterdam,

    River `90 K5, 350, TH700R4, NP241, "32, 3.08, 10 bolt F, 10 Bolt R(GOV-Lock)
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    No, lockup is not hydraulic. Lockup has, in almost all cases (except early diesels) been electric. there would be no wires if it were not electric. Go to a tranny store, and ask for the TCC for your truck. I gurantee you there are wires on it, and that is what locks or unlocks the TCC, electricity. Gear shifting on these years is not electric though..you will get all gears whether or not the TCC wiring is hooked up.


    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  9. River

    River 1/2 ton status

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    It`s hydraulic believe me. The solenoid who controls the lock up is electronic (2 wires) but the solenoid is only opening or closing a hydrolic line in the transmission in o.d. the transmission overrides the solenoid.

    The 4L60E is a real electronic controlled transmission the TH700R4 not just hydraulic.

    Greetings from Amsterdam,

    River `90 K5, 350, TH700R4, NP241, "32, 3.08, 10 bolt F, 10 Bolt R(GOV-Lock)
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Ok, I thought you meant that there basically was no solenoid input. As a matter of fact, you can convert the 700 to hydraulic only lockup, in all cases, by putting a check ball in the snout of the TCC. You are correct, hydraulic pressure is what engages or disengages the converter clutch. But without the TCC working correctly, it is "open" thus no lockup, because the fluid is not being diverted one way or the other.

    Dorian
    My K5 and Chev/Olds tech/links page: <A target="_blank" HREF=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</A>
     
  11. River

    River 1/2 ton status

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    I didn`t mean without TCC but without the wires off the TCC connected.
    My english is average but when it comes to explain technical things it`s hard to do.

    But we figured it out any way.

    Greetings from Amsterdam,

    River `90 K5, 350, TH700R4, NP241, "32, 3.08, 10 bolt F, 10 Bolt R(GOV-Lock)
     

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