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Technical GM 400 Transmission ?

Discussion in 'The Hokey Ass Message Board' started by 383deuce, Feb 10, 2020.

  1. I am helping a friend get a Model A on the road he bought as a project car from this site. It has a GM 400 transmission in it that has the yoke attached to the tail shaft with a large NUT. So first ? is what was it out of? 2nd ? is can the tail shaft be changed out to take a slip yoke? Thanks for any and all HELP
     
  2. Moriarity
    Joined: Apr 11, 2001
    Posts: 30,777

    Moriarity
    SUPER MODERATOR
    Staff Member

    I believe those are from a truck with a 2 pc driveshaft. there is a slip joint where the 2 shafts meet so one at the trans tail isn't needed. I don't know why it couldn't be changed, but I can't tell you exactly what needs to be done.... good luck, someone here will know
     
    lumpy 63 and bchctybob like this.
  3. Doublepumper
    Joined: Jun 26, 2016
    Posts: 1,534

    Doublepumper
    Member
    from WA-OR, USA

    Last edited: Feb 10, 2020
    lumpy 63 and bchctybob like this.
  4. deathrowdave
    Joined: May 27, 2014
    Posts: 3,518

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    Unbolt the yoke and slip in a new seal and slip yoke and carry on
     

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

    OLDSMAN
    BANNED

    Denny, just as said replace the seal get a standard slip yoke and life will be good
     
  6. ^^^^^ X3 new seal and slip yoke and away you go
     
  7. Don’t toss the bolted yoke. Us truck guys like em.
     
    427 sleeper likes this.
  8. lumpy 63
    Joined: Aug 2, 2010
    Posts: 2,603

    lumpy 63
    Member

    The output shaft on a truck t 400 has a ridge on it which does not allow the passenger car yoke to fully seat in it. Yes the yoke can be shortened to give 3/4" to 1 " of free travel , I have done this several times . I can remember Tim who used to own San Diego Driveline asking customers who would bring in measurements for t400 driveshafts asking ...is it a truck t400 or a car t400?
     
  9. Lumpy is correct, you can't just change the seal and make a car yoke fit, the output shaft has an O-ring on it to keep the fluid in, when you look at the bolt in yoke you'll see it's not splined to the end so it can go over the O-ring. Another supplier for the slip yoke that will fit that trans is Inland Empire Driveline

    https://www.iedls.com/

    The conversion yoke from Inland Empire on the right (about $80 bucks) and regular car non bolt in yoke on left, you can see how it's not splined all the way to the end and it's overall shorter.
    19622.jpeg 19621.jpeg
     
  10. Thanks everyone for all the information.
     
  11. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 778

    Kevin Ardinger
    Member

    I think he said it was held on by a large nut, not a bolt. That is something different. Maybe a large truck or motorhome trans. I’ve never seen one with a large nut unless it had a parking brake on it. Those had straight cut gears if I’m not mistaken.
     
    mohr hp likes this.
  12. mohr hp
    Joined: Nov 18, 2009
    Posts: 929

    mohr hp
    Member
    from Georgia

    TH 475
    Basically a 400 for heavy use.
     
    Kevin Ardinger likes this.

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