TH400 trans rebuild

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

  1. Luxus

    Luxus Gold Level Contributor

    Well, I checked the rear end play and it's in spec. But the middle two are way out. At least acording to the article. Fyi I got a bushing with a lip so it wont walk.
     
  2. Bens99gtp

    Bens99gtp Well-Known Member

    1969RIVI likes this.
  3. 1969RIVI

    1969RIVI Well-Known Member

    Too late for me but if I ever have to pull the trans out and apart again I will be putting this in!
     
  4. Bens99gtp

    Bens99gtp Well-Known Member

    Hey I've been building my own transmission for 20 years now and never knew of this.

    But as I stated, I'm no profession just been shown and learned a few things along the way

    But also never had a failure in this area either......maybe I've just been lucjy
     
  5. 1969RIVI

    1969RIVI Well-Known Member

    Hey the day we stop learning is the day the world officially sucks! Being a pro or not you've helped me immensely and for that I'm thankful. I learned alot doing that rebuild and I would and will do it again someday and the knowledge you passed to me will come in handy again!
     
  6. Luxus

    Luxus Gold Level Contributor

    So from reading the CK article, it seems to me that GM didnt care if the reaction carrier had some float to it. And seems you guys have been building trans for years without really worrying about this and every thing has been OK.

    On the other hand there is some logic in 'tightening things up' on a trans that is being built up to handle more power. There doesnt seem to be a reason to not do it.

    I will say that CK thing wont work for me. I dont really want to go get my carrier machined. More time, money and hassle. I did find a place that sells shims that go under the 4 tang washer. If I decide to do it, that will be the route I take.

    https://transmissioncenter.net/shop/shim/
     
  7. Bens99gtp

    Bens99gtp Well-Known Member

    Those should work too.

    I'm running mid 10s and having no issues the way gm did it. But that doesn't mean there isn't some gains in keeping things better inline and by reducing friction.


    I'm doing me my next one this winter, going to try to find a gear set that has low 2.3 or upper 2.2 1st gear.......my 4.30s are a touch aggressive sometimes on not very well prepped surfaces, but are spot on going out the big end........so I'm thinking if I can tame 1st down s touch I might be a little more consistent. Plus I'm going to try to put some aluminum drums in it to lighten things up
     
  8. Luxus

    Luxus Gold Level Contributor

    I'm working on the front pump and I'm inspecting the pump gears. The outer gear clearance is good I think. I'm measuring 0.004 - 0.005". The inner gear I'm not so sure about. I'm measuring the clearance between the teeth and the crescent. I'm seeing at least 0.015". Hard to be exact because of the curve and the feelers get stiffer that thick. The pump body face to gears is good I think. My smallest feeler gauge is 0.0015" and I can barely get it in between a straight edge and the gear.

    Should I be worried about the clearance on the smaller gear?
     
    Last edited: Dec 8, 2019
  9. Matt69olds

    Matt69olds Active Member

    Put the outer gear on a flat surface. Drop the inner gear in the outer gear teeth. Place a finger in the inner gear opposite where the teeth are meshed together and drag it across the workbench. If you can drag the outer gear with the inner gear and noth have the teeth become unmesshed, and all the other inspections and measurements pass, I’d reuse them. An old timer showed me that trick it seems to make sense.
     
  10. Luxus

    Luxus Gold Level Contributor

    Interesting. I'll try that and let you know what I find.

    I will say that visually and by touch they dont seem to be worn.
     
  11. Luxus

    Luxus Gold Level Contributor

    Well my gears passed your test Matt. Another good sign but that biggish gap still bugs me a bit. I found out that a new set of gears is just $12. For insurance I am going to buy a new set and see how they fit. Might be a waste of money but it's only $12.
     
  12. Luxus

    Luxus Gold Level Contributor

    Just checking in. All the drums are in and the front pump is rebuilt and installed. I assume I should disassemble the valve body completely to clean it, correct? I'm talking about pulling the pins and pulling out all the valves.

    BTW new pump gears have the same kind of gap as the old ones, so I'm going to assume it's normal. I put the old ones back in.
     
  13. 1969RIVI

    1969RIVI Well-Known Member

    I did, it doesn't take long or much effort to pull it all apart, clean it and put it all back together again
     
  14. Bens99gtp

    Bens99gtp Well-Known Member

    Correct, just a good cleaning if not performing any other changes........just do 1 at a time and pay very close attention to order and direction the valves come out. Sometimes there are several in each bore and flipping them is a bad thing
     
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  15. Luxus

    Luxus Gold Level Contributor

    So I took apart the valve body, cleaned everything and put it all back together (correctly hopefully). But of course there was a problem. The first pin I pulled had a spring loaded piece behind it and the little cup looking part went flying. I haven't been able to find it since. You guys know what that thing is called? If I cant find it, I'll have to buy one.
     
  16. 1969RIVI

    1969RIVI Well-Known Member

    I would keep looking for that valve body plug. I'm not sure if you can buy those separately or if you'd need a donor valve body to source one from? Maybe another member that does lots or trans builds has a spare in their tool box they would mail to you?
     
  17. Matt69olds

    Matt69olds Active Member

    What bore did the plug come from? I might have a junk valve body I could get a replacement for you
     
  18. Luxus

    Luxus Gold Level Contributor

    20191228_165919.jpg it's the big one on the left. The one where the pin is not all the way in.
     
  19. Bens99gtp

    Bens99gtp Well-Known Member

    If no one jumps in I'm sure I have a couple sitting on the shelf, wont be in the shop till tuesday though. But I can get you one in the mail then if someone doesn't by then
     
  20. Matt69olds

    Matt69olds Active Member

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