TH400 no shift to 3rd at WOT

Discussion in 'The "Juice Box"' started by 70_GSX_Clone, Sep 3, 2013.

  1. 70_GSX_Clone

    70_GSX_Clone New Member

    Background:

    I built a 70 GSX clone back in 1995. The setup I had worked great for many years. Had the engine out recently for some fixes and thought I would have the transmission gone through. I told them to leave the VB alone because it had a shift kit in it and loved the way it worked. I'm am looking for my invoice to tell you what all they did but in the end it was a lot. Pretty much an entire rebuild.

    Got everything back together and broke in and started testing and tuning things.

    Current issues:

    Issue #1

    I did have a shudder from 1-2 under medium to heavy throttle but no issues under light load or under WOT. I did have the modulator screw turned in about 1.5 turns to the right for a firmer shift and later low throttle shift points. I backed that out and tested it some but haven't fully tested it to see if that issue is gone totally.

    Any thoughts on that?

    Issue #2

    The shifts for 1-2 and 2-3 used to be at 4600-4800 at WOT.
    Now the 1-2 was 5200, and I let it go to 5200 but couldn't stand to let it go any higher to see where 2-3 happened.

    I had another governor so I swapped one in with heavier weights.
    The shifts for 1-2 were at 4400 but let it climb to 5200 and still no 2-3 shift

    I put a heavier spring on one side to see what that would do.
    The shifts for 1-2 are at 3500 but still no 2-3 shift.

    I saw mentioned a number of times in the forums the B & M governor calibration kit but seeing how it is shifting at such a low rpm for 1-2 with a weight and spring change already that perhaps I need to look elsewhere for the 2-3 WOT shift issue.

    Any thoughts on that?
     
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    I initially thought that your governor might be a little sticky, but the same thing happens with 2 different governors so that is out. The modulator only adjusts the minimum and part throttle shift points, so that isn't it. It sounds like a valve body problem, maybe a sticky shift valve or something of that nature.
     
  3. 70_GSX_Clone

    70_GSX_Clone New Member

    LARRY70GS, thanks for pointing me in the right direction. We dropped the valve body as you suggested to check things out. When we took it down we found that the transmission shop had put one of the balls from the original B & M shift kit in the wrong spot. It was stuck up behind the gasket somewhere and when we took the gasket down it finally fell out. We checked all the valves just to make sure they moved freely but they were all fine. We put it back together with some new gaskets and the balls in their proper place and the thing shifts great. Shift points back to 4400 and 4600 and nice and firm like it used to be. Thanks again.
     
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    You're welcome. Glad you got it sorted out. I got this thread confused with the one by cobraed in the 400-430-455 engine foruum.:laugh: Disregard my e-mail.
     
  5. cobraed

    cobraed Active Member

    70-GSX-Clone,

    About two months ago, my son bought a beautifully restored white 70 GSX clone from a guy named Mark here in virginia. It looks just like yours from your avatar. He is having the exact same problem with the 2 - 3 upshift that you had Can you please take a couple of minutes to read my link below and let me know your thoughts and any recommendations you may have.

    http://www.v8buick.com/showthread.php?273102-No-2-3-upshift-at-full-throttle


    thanks
    Ed


    .
     
    Last edited: Sep 19, 2013

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