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THM 125C Torque Converter Clutch Solenoid Replacement.

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    THM 125C Torque Converter Clutch Solenoid Replacement.

    OK here is the procedure to replace the TCC solenoid on a THM 125C 3-speed automatic transmission as used in these A cars.
    The pictures I took of a spare transmission in my basement, so the procedural description will vary for a transmission in a car.

    Start by supporting the left-front of the car on a stand and removing the wheel, splash panel, and any wiring harnesses obstructing the transmission end-cover.
    Most of the work will be done through the fender area.

    Remove the end cover using a 13 MM socket.

    Remove the single Torx bolt retaining the TCC solenoid,

    Cut the wires close to the old solenoid and discard it. New solenoid will have a splice kit included.

    Lubricate o-ring on solenoid nipple with miscible grease and install. Install bolt and torque to 11 LbFt (14 N-M)

    Install new gasket on end cover if necessary; and replace cover. Use no sealant other than Copper Spray gasket adhesive. Use blue removable-strength Loctite on bolts if desired. Torque bolts repeatedly until they will all hold 10 LbFt torque. (13 N-M)

    In 1987 they installed a screen in the charge pump cover to protect the solenoid, but it requires machining the cover to accept into older transmissions.

    The new solenoids sold today have a larger exhaust hole and allows the valve to return to unlocked position with less back-pressure.

    This should fix you up! Sorry for the crappy pictures but this was done in the dark with a weak LED flashlight.

    http://68.209.87.173/125C_TCC/125C_asm.jpg Cover that will be removed.
    http://68.209.87.173/125C_TCC/125C_cover_off.jpg Transmission with end cover removed.
    http://68.209.87.173/125C_TCC/TCC_Sol_Annotated.jpg Solenoid installed on valve body.
    http://68.209.87.173/125C_TCC/TCC_So..._annotated.jpg Close view of place where solenoid mounts.
    http://68.209.87.173/125C_TCC/TCC_Solenoid1.jpg Close view of solenoid.
    http://68.209.87.173/125C_TCC/TCC_diagram.jpg TCC valve diagram drawing.

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    #2
    looks good and detailed.
    send the a link to are adim and he sould put in in the Knowledge Base. so we can have it for ever

    Originally posted by LordDurock
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      #3
      This is great help! Thank you very much for taking the time to assist!

      Also very helpful information here:

      Originally posted by Pontiac6ksteawd View Post
      Hey Tuddi. Yes you can replace the TCC solenoid WITHOUT taking the tranny out. In the following link is complete instructions on how to replace the TCC solenoid on the 3 speed tranny. Althou this is in a Pontiac Fiero, the same EXACT procedure applies to a A-Body car, except the A-body car is a slight bit easier to work on in this area.

      http://www.kichline.com/chuck/fiero/TCC.htm

      Other than the directions there, you will need the TCC solenoid, the one linked above somewhere, the tranny side pan gasket (or RTV if all else fails). You dont have do drain the tranny, and will loose maybe a 1/4 pint when you pull that tranny side pan off. I have done this repair befor, having never worked on a tranny befor. it took all of 90 mins to take it apart, and, put it back together.
      Thanks for that Brian!
      Last edited by Tuddi; 12-29-2007, 01:12 AM.
      Old like good wine...

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        #4
        Do you need to drain the fluid for this?

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          #5
          Nope. Leave the fluid alone. Its in the lower pan, and you are only removing the side pan.
          Brian - Carpe Diem

          I dont have to love my president, or any god, to love my country!!
          More people have died in the name of "God" than in all wars combined thruout history
          01 Pontiac Aztek GT AWD 127k - 04 GMC Envoy SLT XUV 193k

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            #6
            Yay this is awesome!! I need to replace both the TTC Selonoid and the pressure swtich on mine, of course I have to get it on the road again

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              #7
              Wait, ok so I have a 1987 Chevy Celebrity Eurosport that I believe needs the TCC Solenoid. From what I read I have to do all of this work like removing the ball joint, cross member etc..So I don't actually have to do that with this car? I can get to it by unbolting the cover? This would save me a lot. They quoted me $525 to do this. If it isn't this easy I'm just unplugging the damn thing because I can't afford it. I have the 3 speed auto as well.
              Last edited by Mathias; 03-01-2008, 04:24 AM.

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                #8
                If you have a 3-speed 125C tranny it is easy, remove only the pan to access this.

                If you have a 4-speed 440T4, the left side driveshaft goes through the end pan and also the pan is too deep to clear the charge pump. You will have to remove the CV driveshaft at least and MAY be able to bet the pan off if you lower the cradle on the LT side.

                A 125C can live w/o a TCC, but a 440T4 CAN NOT live without it.

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                  #9
                  Awesome thanks turbo. This is what happened. I was driving the car on the highway for about 45 minutes. Got off the highway and the car started shifting hard like it was slipping but only under 45. I pulled into a gas station because of the way it was acting and the car stalled out after kind of jerking to a stop. I got gas and started the car up and it shifted fine from then on until I got back off of the highway again. Same thing happened. Sound like the TCC solenoid?

                  Comment


                    #10
                    No problem. That sounds like a classic case of sticking TCC solenoid. There have been several threads posted with pictures etc. of this repair. I'll re-post some of it here with a few pictures incase you didn't see them!

                    Look at these threads:
                    http://www.a-body.net/forums/showthread.php?t=58
                    http://www.a-body.net/forums/showthread.php?t=67

                    They show a "yoke" or bracket around the end of the tranny. I think this is only on 4-cyl cars. I have never seen a 6-cyl A-Body with 125C that had the transmission end cover obstructed. I don't think you will have to take off the suspension; just the left front tire.

                    It's been a while since I did any in-car work on a 125C. I converted to a 440T4 because the 125C break so aften from lead foot and turbo boost.

                    This is what the new solenoid should look like:


                    Here's the valve train the solenoid operates:


                    Here are some pictures of a tranny I took apart to show this. It is one of the many junk ones laying around that turbo-intercooled 3.1 break badly...

                    Complete trans (on floor):


                    End cover off:


                    Parts labelled:


                    Closeup of mounting location:


                    Hope this info is useful!
                    David
                    Last edited by turbokinetic; 03-01-2008, 01:14 PM. Reason: Pictures - (missing several)

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                      #11
                      Originally posted by turbokinetic View Post
                      OK here is the procedure to replace the TCC solenoid on a THM 125C 3-speed automatic transmission as used in these A cars.
                      Thanks...what's the relative cost for a Kit or parts needed?

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                        #12
                        It's been a while since I bought one - IIRC it was about $30 for the solenoid and a dollar or 2 for the end cover gasket.

                        Tried to look it up online but the site is down. :-(

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                          #13
                          I note that one of the guides quoted by turbokinetic gives instructions to disassemble a portion of the suspension and raise the engine in order to get to the valve body. Is it necessary to do this? I have an '87 Cutlass Ciera with the 2.5 and THM125c. I'm afraid that disassembling part of the suspension will affect its alignment.

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                            #14
                            No you dont have too on a 3 speed tranny, which you have..

                            Now if you had a 4 speed, thats a diferent story...
                            Brian - Carpe Diem

                            I dont have to love my president, or any god, to love my country!!
                            More people have died in the name of "God" than in all wars combined thruout history
                            01 Pontiac Aztek GT AWD 127k - 04 GMC Envoy SLT XUV 193k

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                              #15
                              OK, thanks. That's weird, though. The guide (this one: http://www.a-body.net/forums/showthread.php?t=58) specifically says it's for the 125c and it claims you need an engine support fixture.

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