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Changing to a th400 from a 700r4, what needs to be done?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by rocko, Apr 9, 2003.

  1. rocko

    rocko 1/2 ton status

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    I'm picking up a TH400/205 combo... what needs to be done in order to get it to work, The truck has a 700/241 in it now. I know the 700 had the TV cable.. what does the 400 have that i'll need to install?

    And the 205 i'm buying is a slip-yoke 205, how hard is it to convert to a fixed yoke?
     
  2. 4x4k20

    4x4k20 1/2 ton status

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    you will need to do away with the tv cable and run a vacum line. also you will need a kickdown switch for a turbo 400 it mounts down at the gas pedal it has one wire the runs down to the transmision best thing to do is find one in a junk yard off a turbo 400 truck . also you may have to do a little driveshaft work because the 400 is about 2 inches shorter than the 700r4. and on the rear 205 i think ord sells the swap kit for this .
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    You'll have to do quite a bit of driveshaft work if you swap to a fixed-yoke 205. Obviously your 700R4 has a 208 or 241 behind it and those are both slip yoke transfer cases. The new fixed yoke design will require an entirely different type of rear driveshaft. /forums/images/graemlins/smile.gif

    Other than that, like said above, vacuum modulator line is necessary, and kickdown switch if you want it to kick down when you kick it in the ass.
     
  4. 90K5

    90K5 1/2 ton status

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    why would that require a totally different type of driveshaft? the yokes on the shaft are the same on each driveshaft, just different on the t-case. might need lengthened or shortened depending on how the length of the 205 affects it
     
  5. 84_Chevy_K10

    84_Chevy_K10 Banned

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    A fixed yoke transfer case will require a slip spline within the shaft. That will basically require a whole new shaft, unless you simply use the tube and one end, and weld the slip spline on the front. Since that's about $175 for just that one part, I think you'd be better off finding a driveshaft and having it shortened and balanced so it'll work with your rig.
     
  6. rocko

    rocko 1/2 ton status

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    Thanks everyone... this is a good starting point for doing my conversion.
     

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