67 ST400 guts compatible with 65-66 ST400 case?

Discussion in 'The "Juice Box"' started by GranSportSedan, Jul 24, 2018.

  1. GranSportSedan

    GranSportSedan Puppet dictator, wife has all power

    I have a brand new rebuilt 67 variable pitch 400 trans, all the good stuff inside and never even had fluid in it yet. I also have a 65-66 nailhead ST400 case and i'm wondering if I can have the guts of the new rebuilt trans installed in the older 400 case.

  2. wkillgs

    wkillgs Gold Level Contributor

    It was 1984 when I built my '66 ST400, so I'm a 'little' hazy on the details...
    There were some changes around 66-67.
    The early trans used an intermediate sprag, the later ones went to a roller clutch. The sprag is the preferred design, you can get a performance one with double the amount of elements (34 vs 16?) for more holding power. You also need to use the drum that was made for the sprag style.
    The center support in the 66 lacked the snap ring that helps keep the support from moving around and damaging the case. The 66 case can be machined for the snap ring.
    Filter style changed. You can use the later filter, but need to drill/tap the valve body for the filter support bolt, or maybe use a later valve body.
    Again, I'm unsure if these changes were made for 67, but you can look into it.
    And you know about the different size yoke and tailhousings used on the early ones.
  3. GranSportSedan

    GranSportSedan Puppet dictator, wife has all power

    my 67 trans has hd intermediate sprag, later valve body and filter assy.

    BRUCE ROE Well-Known Member

    The 67 guts will interchange with 65-66. The cases don't change for a long time,
    the center support backing ring is machined into the center section. The old type
    center section might be machined, or use a newer one. I believe this change was
    some time in 69.

    The newer style filter/pan only came in late in 67, case not affected but require a
    5/16 threaded hole in the valve body, have added it myself to an earlier trans.
    The output shaft doesn't change although there is the O ring or non style. The
    outer tail housing can be swapped without taking the trans apart, for different
    yoke dia. And I think there was an early style governor with different support
    shaft arrangement, never ran into it here.

    I have encountered cases with only 6 front pump bolts. But the casting had the
    metal, so I ran a tap in and converted to 8 bolts. Of course a lot of different bell
    housings were used for different engines, Buick went BOP by 67, Cad by 68. SWP
    big Olds had no speedo output. Bruce Roe
  5. wkillgs

    wkillgs Gold Level Contributor

    I checked my source, the 'Turbo Hydramatic 400 Transmission' book by Ron Sessions.
    The 16 element sprag was used 64-70, the less desirable roller clutch started in '71.
    Center support... Bruce got it, 1969-earlier should either use the later center support or machine the existing one for a 0.040" spacer ring. his prevents wear/damage to the case.
    GranSportSedan likes this.
  6. Bigpig455

    Bigpig455 Fastest of the slow....

    One other thing that should be talked about is the valve body.. The 67 Valve body has a tiny 2-3 shift valve as detailed in Mark DeConti's article (http://www.buickperformanceclub.com/SPTrans.htm)
    I too have a 66 ST400 I'm looking to eventually build, and in the parts I've been saving I have a valve body from one of my favorite transmissions, a 71-72 big Olds OR TH400.. I've actually has a couple of these transmissions, you can modify shift points and firmness but the 2-3 kickdowns are like the car is telepathic...

    So they question is: are there any specific modifications to installing a later valve body, other than using a later filter, bolt and support? Mark's article doesnt mention any. Has anybody tried a big car valve body swap? what was the result?

    BRUCE ROE Well-Known Member

    You can put any valve body + valve plate combination on any 65 up TH400. I
    generally use an early 70s transmission (of course from a big block ap) and
    convert it to a switch pitch plus a few other upgrades. The switch pitch valve
    bodies are not considered best. The later valve body set will work in the early
    trans without modifications. Bruce Roe
    Last edited: Jul 28, 2018
  8. telriv

    telriv Well-Known Member

    On any TH400 except 1964.

    BRUCE ROE Well-Known Member

    Right 65 up. Forgot on last post, but updated it. Bruce
  10. GranSportSedan

    GranSportSedan Puppet dictator, wife has all power

    So to just confirm one more time. I should be able to install all these components in the 65 transmission case and the only thing I'm going to have to worry about is checking for proper clearances?

    BRUCE ROE Well-Known Member

    As I recall about the only thing to redo is the input and output end play. Check
    that the governor shaft is the same. There are few tricks putting these together.
    good luck, Bruce Roe
    GranSportSedan likes this.

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