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TH 400 Disassembly

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rockink5, Apr 25, 2003.

  1. rockink5

    rockink5 1/2 ton status

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    Trying(key word) to tear down a 400 to swap cases. I have gotten to the point where I need to remove the last section, I believe this is the planetaries. How do I get it past the snap ring /forums/images/graemlins/angryfire.gif. After I get this I can start reassembly. Any help would be nice. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif
     
  2. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    special tool needed
    its like an arbor press, but foot operated. it presses down on the gear set and then you can use your hands to pull out the snap ring. call around to your tranny shops in town and see if they can do it for ya.
    grant
     
  3. K5 NUTT

    K5 NUTT 1/2 ton status

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    What grant said....i have a universal one at home to do that job of compressing the paltes..

    Does this mean you have some spare 400 parts laying around...i need the planetaries...a thrust washer in mine wore out in the planets...that metal took out the torrington bearing and rendered the palnets useless...

    DW /forums/images/graemlins/usaflag.gif
     
  4. 82GR8WHITE

    82GR8WHITE Registered Member

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    Hey Nutt
    Do you need planetaries. I have a TH400 that is working and I am putting it in place of a 700r4 backing a 6.2. In my th400 tranny build up I am putting in some straight cut planetaries. . /forums/images/graemlins/rotfl.gif I can probably sell you the helical plantearies that I will be pulling. Let me know /forums/images/graemlins/ears.gif It will give me an excuse to start on this project.
    Also I have to get rid of the burnt 700r4... it is rebuildable... it still has reverse and low.
    James
     
  5. K5 NUTT

    K5 NUTT 1/2 ton status

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    allready have 2 core 700R4's in the garage...
    i believe straight cut gears in the 400 denote that it came froma TH475....just put one of those in the burb to replace the torn up planets in the 400.

    DW /forums/images/graemlins/usaflag.gif
     
  6. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Whoa, hold on.
    I've rebuilt my th400 a few times and never needed an arbor press or anything.
    [ QUOTE ]
    I have gotten to the point where I need to remove the last section, I believe this is the planetaries. How do I get it past the snap ring

    [/ QUOTE ]
    I'm not quite understanding you here, but it sounds like you have taken out the foreward clutch assembly, and behind that, the direct clutch assembly and the 2nd gear band...
    You may have even gotten as far as popping that first snap ring off and pulling out all the intermediate clutches.. then behind that is the center support where you have to remove a snap ring AND there is 1 bolt that requires a 12 point 3/8" socket to remove the bolt that holds the center section to the case...
    Th350's don't have this but the th400 has this bolt. /forums/images/graemlins/crazy.gif

    As for the snap rings, a good set of picks works great, and usually a long straight screwdriver if you twist against the case it will pop the snap ring out. /forums/images/graemlins/thumb.gif

    If you're swapping internals between th400 cases I would highly reccomend getting a manual! I have 2 different versions of the ATSG manual which both do a great job of walking you through the teardown and rebuild of a tranny. You can get these manuals for about $25 in the transmission section of the jeg's catalog. /forums/images/graemlins/thumb.gif
    If you know what you're doing you could rebuild the tranny off this diagram alone:
    [​IMG]
    [​IMG]
    If you've already gotten past this:
    [​IMG]
    Then the tapered snap ring and this is the bolt you have to remove next, then the geartrain will pull out:
    [​IMG]

    Now theres a few little tricks to putting one back together also... Like the first tapered snap ring that holds the center section, you will put the gap at 9 o clock, THEN torque the center support bolt to 22 ft.lbs as you stick a screwdriver in one of the other holes and try to rotate the center support counter clockwise as you tighten the center support bolt. Then the intermediate clutches and the next flat snap ring gap at 3 o clock.

    Good luck. /forums/images/graemlins/thumb.gif
     

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