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  • TH400 Questions

    I'm looking for some advice on a th400. When the car that it is in was bought the trans shifted firm, chirping the tires on the 1-2 shift. Since that point the engine has been freshened and a small stall converter put in. Now when accelerating with the pedal to the floor it will shift lazily at ~3500rpm whereas before it was shifting around 5k. In normal driving conditions it will shift as it should. I'm thinking it may be something in the vacuum line, but I'm clueless when it comes to this stuff. Has anyone ever dealt with something like this?


    Sent from my iPhone using Tapatalk
    2002 Trans Am WS6
    Pacesetter lt's
    OR-x with 10 series flowmasters
    C6z chrome wheels

  • #2
    Google search modulator valve vaccume issues.
    2006 Suzuki gsx-r600, blue & white, Two brothers exhaust, K&N... for sale. $3,500 firm.
    1991 Ford Mustang GT, red, 5 speed, almost finished...

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    • #3
      ^ What he said.
      http://www.youtube.com/josephflynn007
      Many vehicles for sale
      Money can take you far, but respect can't be replaced.


      because you buy what you like, not what some jackass on KYHP likes....

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      • #4
        im no help what so ever but hope you get her lined out and whats the trans in??
        03 mach1 5.3 stroker crower cams and some spray 334n/a 464

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        • #5
          Originally posted by Sweet072k View Post
          Google search modulator valve vaccume issues.
          Thanks! I found a couple good articles that put me on the right path


          Sent from my iPhone using Tapatalk
          2002 Trans Am WS6
          Pacesetter lt's
          OR-x with 10 series flowmasters
          C6z chrome wheels

          Comment


          • #6
            TH400 Questions

            I disconnected both ends of the vacuum line and there was no obstruction. From there I used a screwdriver to adjust the modulator valve. I took it two turns clockwise and then hooked everything up and took her for a drive. The shifts were still a little soft but there was a noticeable difference and it revved out better. I came back and took it a turn further and she's doing pretty good now.
            Here's a pic of adjusting the modulator valve for anyone who was as clueless as I was coming into this


            Sent from my iPhone using Tapatalk
            2002 Trans Am WS6
            Pacesetter lt's
            OR-x with 10 series flowmasters
            C6z chrome wheels

            Comment


            • #7
              Oh, and the trans is in a 55 Chevy


              Sent from my iPhone using Tapatalk
              2002 Trans Am WS6
              Pacesetter lt's
              OR-x with 10 series flowmasters
              C6z chrome wheels

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              • #8
                Glad you found your fix, now back to chirping them tires...
                1999 Camaro HOSS
                2003 Ext. Cab GMC Sierra 2500HD Duramax

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                • #9
                  That's pretty cool. I'm glad you got it working better. I asked my father about your issues and he said to check the modulator valve.


                  I also read some articles on your issue. They said a governor kit is what a turbo400 need to change the shift points, if your wanting to get that in-depth with it.
                  2006 Suzuki gsx-r600, blue & white, Two brothers exhaust, K&N... for sale. $3,500 firm.
                  1991 Ford Mustang GT, red, 5 speed, almost finished...

                  Comment


                  • #10
                    ^ right. The way I understand it, the modulator valve controls the firmness of the shifts (to an extent) and whether the trans holds in gear until the governor makes it shift. I'm thinking a lighter inner weight on the governor may be in order soon.


                    Sent from my iPhone using Tapatalk
                    2002 Trans Am WS6
                    Pacesetter lt's
                    OR-x with 10 series flowmasters
                    C6z chrome wheels

                    Comment


                    • #11
                      pics of the car,,,,
                      03 mach1 5.3 stroker crower cams and some spray 334n/a 464

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                      • #12
                        I need to take some good ones. I may do that tomorrow morning


                        Sent from my iPhone using Tapatalk
                        2002 Trans Am WS6
                        Pacesetter lt's
                        OR-x with 10 series flowmasters
                        C6z chrome wheels

                        Comment

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