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th400 output shaft

Discussion in 'The Garage' started by muscle, Apr 12, 2005.

  1. muscle

    muscle 1/2 ton status

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    what should the lenth of the output shaft be on a th400 4wd? the one i have measures 3 1/2" from the end of the case to the end of the shaft. this will be for a th400/np208 setup.

    what i am seeing is the adapter housing on my th350/np208 takes up roughly 4 inches. the adapter plate i got off the junkyard today to convert to a th400/np208 is only 1 1/4" thick. so the way i see it ,the output shaft is too ong on the new th400 i got. Or is there a differant adapter out there i need?
     
    Last edited: Apr 12, 2005
  2. muscle

    muscle 1/2 ton status

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    so the type of transfer case you bolt on determines the output shatf length? I told the guys at checker i needed a th400 for a np208.
     
  3. joefl

    joefl 1/2 ton status

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    There is 3 lengths of output shalfs for the th400 4x4's. Not sure on the 3 1/2 length, but I would think it is the 208 output. The adaptor you got is probaly for a np203.
     
  4. sweetk30

    sweetk30 professional hooker Premium Member

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    second this info. most 208 addaptors i have seen are much thicker.
     
  5. muscle

    muscle 1/2 ton status

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    a picture of a th400/208 adapter would help alot if someone has one
     
  6. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I'm not trying to start anything but in this thread - http://coloradok5.com/forums/showthread.php?t=135169 - you said you got the TH400 by accident after ordering a TH350. :confused:

    What ever the case is since you're uncertain about the tranny take the part number off of the crate/box, go to a different Checker and have them tell you what it fits. The tranny could be misboxed but it could also be a case of the part number being one digit wrong than what you were suppose to get and no one caught it.

    As for the pic of an adapter, the correct one for you may depend on year. For a 205 application, the change in 85 from the tall to a short adapter also effected the TH400 tailshaft length - this type of change may apply to the 208 version as well.
     
  7. 70~K5

    70~K5 1/2 ton status

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    From ORD's web page................

    GM TH400 Automatic Transmission:
    If you have a TH400, there are three options for mating the 203 to your trans.

    1: Use a factory configuration. The TH400 was available with the NP203 in heavier duty trucks (3/4 and 1-ton generally) in approximately '78-'79. The factory configuration uses a 1 3/8" stickout 32 spline shaft in the TH400, a 32 spline input gear in the NP203 and a 1.1" adapter plate between the two, somewhat similar to the TH350 adapter plate. This is the shortest way to mate the TH400 and NP203.

    2: Use a TH400 that originally had an NP208 mated to it. This TH400 uses a 32 spline shaft that sticks out of the case about 2.5" and has an adapter housing that's about 2.5" thick. You'll use a TH400 version 32 spline input gear in the NP203 and re-drill and tap the face of the NP203 with the round bolt pattern to match up to the NP208 adapter housing. Benefits of this kit are the parts are quite common since the NP208 was very widely used with TH400 trannies. The drawback is the adapter is about 1.5" longer than the shorter factory configuration.

    3: Use a TH400 that originally had a NP205 behind it. This TH400 uses a 32 spline shaft that sticks out about 4.5". You'll need to use a factory TH400 to round pattern NP205 adapter housing that is 4" thick and once again, re-drill the front face of the NP203 to match the round pattern. The input gear will be the TH400 version NP203 32 spline input. Drawbacks to this system are the overall length with the 4" housing between the two and the expense of buying the factory housing. They're not common as used parts and typically must be purchased new. ORD can supply this adapter.
     
  8. R72K5

    R72K5 Banned

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    ive got an 86 k20 out here with th400 and 208 i can meausre if needed,.

    have access to an 82 k10 with th350 and 208 also, it was a 700r4


    good luck
     
  9. muscle

    muscle 1/2 ton status

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    if you could please measure to distance between the 400 and the 208 which the adapter provides i would appreciate it.

    i been to the salvage yards today and seen alot of 350/208 adapters which are approx 3 1/2" wide. but no luck finding a 400/208

    as for the mistake checker made on the tranny I spoke to the manager and since there was a delay involved in receiving the tranny he thought he would make up fot it by substituting a 400. which is great although i will need to revamp alot of things to get her in there ;)
     
  10. thebigdaddyof2

    thebigdaddyof2 1/2 ton status

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    Here's the only pic I have of a T400 to NP208/241.

    th400np241adaptor.jpg
     

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