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Technical Tailhousing for a th425 trans ?

Discussion in 'The Hokey Ass Message Board' started by 296moon, May 7, 2019.

  1. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,422

    OLDSMAN
    BANNED

    Where are the moderators this whole thread is so OT I can’t believe it’s still on here.
     
  2. sdluck
    Joined: Sep 19, 2006
    Posts: 3,185

    sdluck
    Member

  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    I am building a 1960s showrod.

    The question is, why are YOU on this thread, if YOU are not interested in it?

    Maybe you should see if you can get posts and media by @hrm2k removed, too.

    There are a bunch more, too.
     
    Last edited: Jul 17, 2020
    anthony myrick and Ned Ludd like this.
  4. Deuces
    Joined: Nov 3, 2009
    Posts: 23,751

    Deuces

    Let's keep this one going...... I'm very interested.. :)
     
  5. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 3,375

    GearheadsQCE
    Alliance Vendor

    @OLDSMAN,
    Why do you keep saying this thread is off topic? Why do you want it shut down?

    My suggestion to you is go to the upper right hand corner of the screen and click 'Unwatch Thread'
     
  6. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Here is the "smoother" design, as produced, in 6061-T651.

    It takes an OEM bushing, seal, and gasket, straight from a TH400. IMG_20200717_191506.jpeg IMG_20200717_191520.jpeg
     
    Budget36, hrm2k, lumpy 63 and 2 others like this.
  7. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    For perspective about the hair that is being split here (I checked the GM archive, last time I was at the home office):

    This transmission was designed in 1962, developed in 1963, tested in late 1963-1965, in parallel with the TH400, as they (mostly) use the same parts. Yeah, it was not sold until the model year 1966, but it was at the auto shows in 1964, and in showrooms in September of 1965.

    It is 98% identical to a TH400, and in the earliest version, a Buick Super Turbine 400 (switch-pitch 400).
     
    lumpy 63 likes this.
  8. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 3,375

    GearheadsQCE
    Alliance Vendor

    Gimpy,
    That is a thing of beauty. Please keep posting showing the Transmission to QC connection.

    As far as 'On or off topic': "He who lives in glass house should not throw stones."
     
    gimpyshotrods likes this.
  9. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
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    I hope that my posts/threads are not deleted. We do, after all, have an entire section devoted to a transmission that came out in 1982!
     
    Zuffen and Truckdoctor Andy like this.
  10. studebakerjoe
    Joined: Jul 7, 2015
    Posts: 1,136

    studebakerjoe
    Member

    Gimpy, keep posting. I'm sure I'm not the only one that likes to see interesting fabrication/modification. You never know where the solution to a problem you have will come from.
     
  11. Wrench97
    Joined: Jan 29, 2020
    Posts: 679

    Wrench97

    Really nice work and a very informative thread.[​IMG]
     
  12. TrailerTrashToo
    Joined: Jun 20, 2018
    Posts: 1,289

    TrailerTrashToo
    Member

    This is the exact reason why the technical content of the HAMB has dropped off. "Traditional Hot Rods" and "Traditional Customs" exist for the "On-Topic" folks. Sometimes, threads were deleted for good reason, and other deletions are a mystery (to me - The Moderators have a tough job).

    When I give a technical answer, I try to provide links to the information source and part # (And a link of where to buy it). Then I see the usual malcontents post the OT complaints, and shortly later the thread goes "POOF". Next time I say ""E'ff it".
     
    pvfjr, Ned Ludd and chubbie like this.
  13. chubbie
    Joined: Jan 14, 2009
    Posts: 2,336

    chubbie
    Member

    I'm impressed!
    And you guys are light years ahead of me. Just a thought on the tail section.. I have an "american " overdrive that bolts to a 400 case and a short shaft. Would that bolt up to the 425? For sale cheap. LOVE tech brings me back to the HAMB
     
  14. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 3,375

    GearheadsQCE
    Alliance Vendor

    @chubbie,
    Check your 'Converesations'
     
  15. smart folks here
    cool stuff
    glad the guy that doesnt like it is not a mod
     
  16. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    I could make it work, but I only have room for about a 21-inch driveshaft as it is!
     
    hrm2k likes this.
  17. chubbie
    Joined: Jan 14, 2009
    Posts: 2,336

    chubbie
    Member

    I think it said that it adds 17", so it should work right? Thats 4" driveshaft!
     
  18. squirrel
    Joined: Sep 23, 2004
    Posts: 55,931

    squirrel
    Member

    Nice looking part.

    A bit of sandblasting, and it could almost look like an old sand casting, eh? But if it's a show rod you're building, I expect you're polishing the transmission case, as well :)
     
    Ned Ludd likes this.
  19. 4 inch driveshaft would be a double cardan joint, or sometimes called a constant velocity joint.

    Gimpy, nice work on that adapter and the thought process. I am curious to see the whole setup installed and how it all fits and works together.
     
  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
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    I am probably going to hand a pile of money to someone else to polish the case.

    A man must know his limitations.
     
    squirrel likes this.
  21. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 3,375

    GearheadsQCE
    Alliance Vendor

    The guy that polishes QC stuff for me is good, cheap and slow. How much can it cost to send a transmission case to Michigan and back?

    You know the old saying, "You can have it good, cheap, fast, pick 2."
     
  22. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
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    I just need good. I have a spare case, that I can use during the build. It has a chunk missing from the bell, but I have the piece. I may just weld it up. If I pull the guts, it will be easier to manipulate. Those things are heavy!
     
    chryslerfan55 likes this.
  23. revcon1972
    Joined: Apr 15, 2021
    Posts: 1

    revcon1972

    Ok, so how much would you charge to make another one of those beauties?
     
    chryslerfan55 likes this.
  24. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
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    How much? We're talking Jay Leno money.

    This is not currently a saleable individual product, and likely cannot be.

    Firstly, using one requires a second TH425 output, to act as a donor for the governor drive gear. Harvesting that portion of the output is a very difficult machining process to do properly, as it, and the turned-down shaft that it must be interference-fit to, are both hardened steel. I am down to my last two gears, having ruined the rest, along with a pile of tooling in developing the process. These parts are nearly impossible to find loose, and require a whole transmission to harvest one. Those go for about $500, delivered.

    Secontly, there is zero market for these. The long and the short of it is that there is no way to recover the sunk cost in designing these, let alone reproducing them. I have to pay myself, my staff, buy materials, and cover other overhead.

    The only way that this was viable to do as a two-off (soon to be 3, and then done), was to have them be part of a whole-car build, and bundled into that price.
     
    TrailerTrashToo and Budget36 like this.
  25. petetjjj
    Joined: Nov 21, 2016
    Posts: 1

    petetjjj

    Amazing! I just saw this looking for TH425 info. I had the same idea only to make an adapter plate and a shaft the would fit into the TH425 output shaft and have the TH400 output spline. Nice job.
     
    gimpyshotrods likes this.
  26. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
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    If I had to do this over, I would make a custom shaft that fits where the pinion plugged into the transmission.

    It would be more expensive overall, but a lot less work.
     
  27. lilboatsman
    Joined: Aug 30, 2023
    Posts: 2

    lilboatsman

    Looking at the TH400 output shaft, it looks like it has a governor drive gear already. Is it not in the right spot? Not the right size?
     
  28. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    Not the correct diameter, and not in the correct position.

    TH425:
    [​IMG]

    Th400:
    [​IMG]
    [​IMG]

    My setup uses a 4x4 4L80E output, with no gear, as it is electronic, which allows for a longer driveshaft.

    [​IMG]
    I remove the governor gear from the TH425 output, bore it out, and press it on to the 4L80E output shaft.
     
  29. lilboatsman
    Joined: Aug 30, 2023
    Posts: 2

    lilboatsman

    Thanks for showing the difference, I think I've been convinced to make a custom shaft that plugs into the original TH425 output. Sounds expensive. How would you go about attaching it? Weld it on solid? Or try to pin it somehow?
     
  30. Radical Chris
    Joined: Sep 1, 2023
    Posts: 1

    Radical Chris

    I'd like more info on this please!!

    As well as where I can order/buy replacement chains!

    Help a brother out? FB_IMG_1693602133808.jpg
     

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