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how does a lockup converter work?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by xnoahx, Mar 15, 2002.

  1. xnoahx

    xnoahx 1/2 ton status

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    Im going to swap in a th700 and Im wondering about the lockup converter. Does it work automaticly or does it nead input from something. Also, how can I tell if its a lockup converter or not?
     
  2. Overkill

    Overkill 1/2 ton status

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    If it's a 700r4 it is a lockup converter. I believe some are locked by an electronic signal from the computer and some use vacuum to sense when to lock.
    A torque converter is kind of like a centifugal clutch, it has little drag at idle, but when rpm rise the converter drags more and turns the input shaft to the tranny. Even while running down the highway there will be a little slippage in the converter due to the fluid (viscous) coupling that sends power from the motor to the tranny. A lockup converter will lock the viscous coupler inside solid so there is no slippage. What this does is prevent slippage, resulting in better gas mileage and it also reduces heat since the normal heat producing slippage is gone. I am not an expert, only going on theory, haha. If anything here is incorrect I hope someone will correct it. There is also more to it, this is just an overview. Hope this helps.
    How to hook it up all depends on which type you have (electronic or vacuum/line pressure). There are kits to manually lock up the electric ones via a toggle switch. There are some plans where you can build your own switch also. YOu will probabaly have to do a search to find them.
     
  3. Innerpiece

    Innerpiece 1/2 ton status

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    basically there is a plate with friction material, just like in a clutch. Under normal non-lockup ops (1st, 2nd, most of 3rd), there is tranny fluid pressure applied to both sides of the plate, so it doesn't do anything. When the lockup happens (for a 700, it goes 1st, 2nd, 3rd, lockup, 4th), a solenoid closes and there is no pressure applied to the engine side of the plate. So with pressure on one side and not the other, it presses the friction materials together and you get clutch style lockup. Good to know that if the gizmos that tell the tranny to lockup fail, it will revert to non-locked.

    The Gospel as told by the Performance Automotive Transmission Center ... birthplace of my Raptor.
     
  4. jimmy88

    jimmy88 1/2 ton status

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    If your intrested, I got my old 700r4 converter cut in half. I could take some pictures and email them to you. Almost twisted the inside hub out of it pulling tree stumps. Amazing thing is it still worked, just a buzzing sound at times.
     
  5. xnoahx

    xnoahx 1/2 ton status

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    No, i dont need the pics, i think im good to go
     

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