TH400 trans rebuild

Discussion in 'The "Juice Box"' started by Luxus, Sep 26, 2019.

  1. Luxus

    Luxus Gold Level Contributor

    As the driving season is coming to a close for me, I'm starting to think about winter projects. It's becoming clear to me my trans is in serious need of some TLC. I have a spare trans lying around which I'm considering rebuilding myself. My questions to the Buick masters out there is is this something I can do myself? I have no problem tearing an engine apart but I've never done any work on a trans outside of a filter and fluid change. I know there are some specialty tools that will be required.

    Question two is I plan on rebuilding the engine also, but maybe not this winter. But when I do, it won't be a stock 455 rebuild. I would like to get it into the 500 hp/torque range. So what mods to the trans do I do to be ready for that? Or is that getting into a territory where it would be better for a pro to do it?
     
    Nailhead Ronnie and TexasT like this.
  2. 1969RIVI

    1969RIVI Well-Known Member

    I just rebuilt my TH 400 myself for the first time. Theres tons of knowledge and experts on here and if you are somewhat mechanically inclined then you will be fine. You should definitely upgrade the sprag to a 34 element sprag, it has stronger holding power. You can install a transgo 1-2 kit or mod the separator plate and valve body yourself (explained in Ben's thread) to achieve a "free shift kit". Look into getting a custom built JW 9.5" converter, you won't be disappointed at all, trust me!! There's a bunch of free mods you can do to make the trans stronger and more efficient. I will try and post some links for you to get you pointed in the right direction. The first link is my build. I bought good quality parts, built my trans to handle whatever I could throw at it torque and HP wise the first time so I didn't have to do it again down the road when I get my other engine done. My engine build/goal is the same as yours to get the 500hp/tq range.

    http://www.v8buick.com/index.php?threads/rebuilding-my-th400.346849/

    http://www.v8buick.com/index.php?th...-kit-and-a-few-easy-internal-upgrades.342929/

    http://www.v8buick.com/index.php?threads/a-few-really-good-videos-on-th400-rebuild-stuff.346092/

    http://www.v8buick.com/index.php?threads/th400-34-element-sprag.342788/
     
    Last edited: Sep 26, 2019
  3. Luxus

    Luxus Gold Level Contributor

    Thanks for the reply. The videos in particular were very educational. I wound up watching a bunch of YouTube videos. I think I will go ahead and rebuild one myself. For now I got a lot of research to do.
     
    TexasT likes this.
  4. Luxus

    Luxus Gold Level Contributor

    Let the adventure begin! I've started tearing down the trans.

    20190930_205241crop.jpg
    20190930_213853crop.jpg 20190930_205323crop.jpg
     
  5. johnriv67

    johnriv67 Well-Known Member

    Put up as many pictures as possible please! Good luck.
     
  6. 1969RIVI

    1969RIVI Well-Known Member

    Whatever you do make sure your work area and parts are clean clean clean!! One spec of debris can clog a valve and then your into some real fun doing it all over again.
     
    Nailhead Ronnie likes this.
  7. Bens99gtp

    Bens99gtp Well-Known Member

    You have a nice case to work with. That's one with the extra thick ears, thicker pan rails, and stiffening web running down the center
     
    Nailhead Ronnie likes this.
  8. Bigpig455

    Bigpig455 Fastest of the slow....

    Ben - what coded/production year(s) cases had these features? I'm looking at cores to build, and it'd be nice to start with a case like that..
     
  9. Bens99gtp

    Bens99gtp Well-Known Member

    I'm not sure I can answer that, I think they were early in production, 65,66,67. The one I have is a 66 Pontiac cas . But there are some easy external tells. The ears have extra webbing in them.

    I have a couple other pics to add but for reason lately I can only add 1 picture, then I have to wait and come back to edit

    Just did a quick look on craigslist and saw a long shaft Pontiac from a 74, it had this case. So no clue on production
     

    Attached Files:

    Last edited: Oct 3, 2019
  10. Luxus

    Luxus Gold Level Contributor

    I can say for sure the case I have is from 74 because it still has the plate with the date code on it.
     
  11. Luxus

    Luxus Gold Level Contributor

    I made some more progress last night. Some pictures:
    20191002_204228_valve body.jpg 20191002_205524_servo1.jpg 20191002_210512_servo2.jpg 20191002_212839_half out.jpg 20191002_212921_half out case.jpg 20191002_212935_resized.jpg

    I got stopped because my 12 point socket wouldn't fit in the hole. You guys know what size that is again? I gotta stop at lunch to pick one up that I will grind down if need be.
     
  12. Bens99gtp

    Bens99gtp Well-Known Member

    3/8th 12 pt
     
  13. Luxus

    Luxus Gold Level Contributor

  14. 1969RIVI

    1969RIVI Well-Known Member

    That kit is very similar to the one I bought. The red alto frictions and kolene steels are good for performance builds and can handle more than your average stock rebuild clutch parts.
     
  15. Luxus

    Luxus Gold Level Contributor

    So question, does the parking pawl come out or can it stay for the cleaning of the case?
     
  16. 1969RIVI

    1969RIVI Well-Known Member

  17. Bens99gtp

    Bens99gtp Well-Known Member

    I leave it in there unless I have too
     

Share This Page