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TH400 Question

Discussion in 'The Garage' started by SUB-ZERO, Oct 13, 2004.

  1. SUB-ZERO

    SUB-ZERO 1/2 ton status

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    I have a 700r4 with a 305 in my Blazer.I also have a TH400 tranny out of a 2WD 454 Suburban.What do I need to do to install it in place of the 700r4?Will this eliminate the TV cable problem I am having with the new carb and 700r4?
     
  2. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    You'll either need a conversion shaft to go into the 400 to mate with your 27 spline 208 T-case. You have to take the entire tranny apart to do this. You will also need the adapter to mate the 400 to the 208.

    Or..

    You'll need a 208 shaft installed in your TH400. If you do this you will need a 208 t-case with the correct 32 spline input, or swap the input shafts in your current T/C to 32 spline from 27. Again the TH400 will have to be disassembled and the proper adapter to mate the 400 to the 208 will be needed.

    A th400 does not use a TV cable, but does have an electronic switch kickdown. (oen wire to tranny)

    Either way, you will not need to modify the driveshafts. They will work just fine.

    John
     
  3. Nonesuch

    Nonesuch 1/2 ton status

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    the output shaft is different as stated above. There are no conversion shafts available for the transmission unless you have a custom one made /forums/images/graemlins/yikes.gif There are 3 different length outputs for the th400 though. You would need to find the appropriate input shaft to convert your 208 to match the transmission. If the th400 is a 2wd version, you will also have to remove the tailshaft housing.
     
  4. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    [ QUOTE ]
    the output shaft is different as stated above. There are no conversion shafts available for the transmission unless you have a custom one made

    [/ QUOTE ]

    I checked and they do make one.

    Advance adapters has one...
    TH400 to 700R4 version NP208

    And TCI has one..

    TCI conversion page

    John
     
  5. Nonesuch

    Nonesuch 1/2 ton status

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    At $393 dollars, I would say that is a custom. /forums/images/graemlins/pimp1.gif The description does not say the shaft is included, only the adapter. I would check on that if that's the way he goes. AA makes some good stuff but they are expensive. I think you could use stock parts and save yourself some money /forums/images/graemlins/waytogo.gif
     
  6. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Completely agree.

    A TH400 shaft for a 208 is around 100 bucks new.

    A used 400/208 adapter can be found pretty easy too. $50-100

    Either way that 2wd TH400 is coming apart to do it.. /forums/images/graemlins/smirk.gif /forums/images/graemlins/thumb.gif

    John
     

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