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  • Transmission Question

    Hi All

    Does anyone know what happens if you run a TH125c transaxle without the Torque Converter Clutch connection. I don't have a computer on my set up, and still would like to use the automatic.

    Regards
    Paul

  • #2
    Re: Transmission Question

    It won't go into overdrive...Might heat up a little more than usual, but I doubt you'll notice a difference or hurt anything. I ran my Firebird without the lock-up for a while because the new computer did not have the provision to control the solenoid directly. Didn't hurt a thing.
    Bob custom '84 Fiero SE --->>> custom F408
    http://www.madmechanics.com/forum/cu...ilepic37_1.gif

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    • #3
      Re: Transmission Question

      Thanks

      When you say it won't go into overdrive, does this mean I have no third gear or that I have to shift through the the gears (1,2,and 3) manually. I was hoping to run this as a permanent set up. I think I could solve the heating problem with a cooler. I'm hooking this up to a 350 V8. It will probably be a little warmer than usual.

      Any help would be greatly appreciated.

      Thanks
      Paul

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      • #4
        Re: Transmission Question

        In my opinion, that TH125c transaxle will not hold up with a V8 attached to it. You need to look at a TH460 4 speed.
        If you're not confused, you're not paying attention.

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        • #5
          Re: Transmission Question

          The TH460 would definately be the better choice and I think eventually that's where I'll end up, however, I will still have the same problem with the TCC switch not being hooked into a computer. Any advice will be greatly appreciated.

          Regards
          Paul

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          • #6
            Re: Transmission Question

            I know there is an electronic and manual version of the transaxle. The person I would contact regarding electrical stuff would be Duane Cox on this forum. If there is a workaround he will know of it.

            Dave
            If you're not confused, you're not paying attention.

            Comment


            • #7
              Re: Transmission Question

              Check out a standard mod done to the TH700-R4 which will activate the lock-up without a computer.  Summit Racing has the kit for about $40.00 which changes out the pressure switch and re-wires the valve body to allow the lock-up at low engine power.  But the problem is that if you let off the power, it won't switch off the lock-up and it will remain in lock-up as the transmission downshifts (which is bad), if you don't remember to switch it off.  I'm using this same system on my 325-4L, and will design a circuit that will cut off the lock-up voltage as the car slows down, and can be re-set with the push of a button.  I have done this mod to a TH700, and it is fairly easy.

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              • #8
                Re: Transmission Question

                I have a L88 350 setup in my car. I just have a rocker switch with a led in the rocker that lets me know when It's on. This locks up the converter manualy. When I get in 2nd gear I flip it on. When I come to a stop I flip it off.It's smiple and will do untill the 5 speed slides in.

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                • #9
                  Re: Transmission Question

                  That sounds like a good solution. Do you mind sharing the details on where to connect the wires? Do you have to switch off the lock up before you stop or after you stop? I would think it would stall if it stays locked up after you stop.

                  Thanks
                  Paul

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                  • #10
                    Re: Transmission Question

                    You have to turn it off before you stop. If you forget to trun it off you'll know it at about 20 miles an hour or slower. It starts to buck a little. When it does I just let off the brake some and switch the switch and get back on the brake. It sounds worse than it is. If you had to stop it still will. I had to do this once. It just stalled the motor, and I had to put it up into nuteral and restart it.It was like a manual car stopping with it in second gear,without pushing in the clutch. I'll have to look and see how it's wired and post how it's done. I think all it does is jumps the converter lock up together.

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                    • #11
                      Re: Transmission Question

                      You should probably get a transmission repair manual to get illustrations of exactly what you are messing with. There may be only two electrical functions in your transmission, of which one is the reverse gear indicator and the other is the lock-up. I don't know if your starter interrupt switch is internal but it might be. Basically you are providing direct 12 VDC to the lock-up solenoid to activate it, and that is all. But in my case (with the TH700) the kit came with a new low pressure switch that you had to replace in the valve body and wire it in series with the solenoid.

                      The easiest thing that you might do is to search for the correct transmission wire using a multimeter. It would be the only function that will provide a resistance reading of between 0 and 1, as it is reading the resistance of the solenoid coil. Your ground might be in the transmission case, or have a wired ground out of the transmission input plug. I have a perfectly good 125 sitting in the yard with a V6 that I will take to the junk yard some day....if I remember to check the readings, I will.

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                      • #12
                        Re: Transmission Question

                        I didn't hook up the trany it was already done before I got the car at a profesional shop that just does engine swaps and etc.. That's why when I got the chance to buy the car with the 350 already in it I jumped on it. I don't know how they did it a this time. I was just guessing at this point. I have another car I was going to put a 350 in. That's when I ran across this car for less money than the kit was going to be just to start. Yes I'll trace the wires and run my multi meter and check it out better. ;D

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                        • #13
                          Re: Transmission Question

                          When you say it won't go into overdrive, does this mean I have no third gear or that I have to shift through the the gears (1,2,and 3) manually.
                          No, TCC, no lock-up. The trans will still operate as before.

                          Bob
                          Bob custom '84 Fiero SE --->>> custom F408
                          http://www.madmechanics.com/forum/cu...ilepic37_1.gif

                          Comment


                          • #14
                            Re: Transmission Question

                            >>>Yes I'll trace the wires and run my multi meter and check it out better.<<<

                            I checked mine out and received no reading from any of the Three transmission connections. The lock-up must be going through a valvebody switch that is open, and that is why there is no reading. It looks like a standard TurboHydro three pin connection, so all the functions are probably the same in these transmissions (I assume). If you can't find a wiring diagram, you will have to pull the pan and follow the wires. It is fairly simple when you are looking directly at it.

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