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which way should I go

Discussion in 'The Garage' started by muscle, Apr 11, 2005.

  1. muscle

    muscle 1/2 ton status

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    a few months ago I bought a rebuilt th350 from checker and when I finally received it, it happened to be a th400 instead :D . Anyways I didnt rush right back to checker to tell them of their screw-up but now im in a dilemma. The np208 is naturally a 27 spline and the th400 is 32. Also the adapter housing will need to be changed out but Im thinking thats the least of my worries.

    So what is easier... swapping out the input of the 208 or tear down the 400 for a new 27 spline output? What costs am I faced with and where is the best place to go to buy the parts? any other hidden issues other than driveline work?

    I also have a np203 but not sure what the spline count would be on that...
     
  2. kgblazerfive

    kgblazerfive keymaster Premium Member GMOTM Winner

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    Swap the 208 for a 203/205 and fix all your problems. Seriously if you change the trans output and need a good tranny shop I would recommend Canyon State Transmissions they are in Queen Creek, bit of a ride for you. They built my tranny, then put in a new output when I put it in my Blazer and the owner is really cool and his prices are really good, his name is Allen
     
  3. u2slow

    u2slow 1/2 ton status

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    The critical part now is the length of that TH400 output shaft.

    The TH400/NP208 adapter is not hard to find... especially if you can utilize the short (as opposed to tall) version. Its also used with the 4L80E in newer trucks.

    32-spline input gear, or a complete 32-spline NP208 aren't hard to find either. I've heard the NP241 input gear is the same also.
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    The NP208 cases are easy to tear down. All you have to do is swap the input gear on the 208 from the 27 spline to the 32 spline. That is the only difference between the 2 cases.

    When you tear the case apart take the snaprings off that hold the chain gears in place. Remove the gears and chain. Then pull up on the tailshaft and it will come out. Do not dissasseble the rest of the parts on the tailshaft if you don't have to. There are about 80 needle bearings that will drop out and go everywhere. I learned the hard way.

    Harley
     
  5. Jimbo*

    Jimbo* 1/2 ton status

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    Which adapter do you have? Short or Tall? I have a th400 np208 with tall adapter I would sell or maybe trade, but this brings us back to the question of tailshaft length. How long is your tailshaft? I'll measure mine thursday A.M.
    Jimbo
     
  6. muscle

    muscle 1/2 ton status

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    my tailshaft sticks out past the tranny 4" which im thinking is too long. I ordered this th400 tranny from checker for a np208 but i dont think they got it right. i started a new post on this issue and am seeking some info for the length needed for the th400/np208 setup. i can go short or long foot because i have both types of crossmembers, the flat and two hump style.
     
  7. Jimbo*

    Jimbo* 1/2 ton status

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    Hey Muscle, I just got back from the shop where I measured the tailshaft at 2 1/4 inches. Looks like my setup won't work for you after all. Sorry. :(
    Jimbo
     
  8. fatbob

    fatbob 1/2 ton status

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    HTML:
    400 to 203 = 1 3/8", 1.1" adapter
    400 to 208 = 2 1/2"
    400 to 205 = 4 1/2"
    I got this info from another board, but it looks like it would be easiest to go with a 205 :grin:
     

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