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TH400 swap???

Discussion in 'The Garage' started by oll' bessy, Feb 11, 2007.

  1. oll' bessy

    oll' bessy Registered Member

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    i have a '75 silverado 10 with a 4 speed (SM420?) and i want to put a TH400 in it. it has a 205 t-case. will the TH400 hook up to the 205 or do i need to change input/output shafts? i know i will need a different adapter plate to. an input on this swap would be great, thanx.
     
  2. oll' bessy

    oll' bessy Registered Member

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    no takers?? am i in the wrong forum here?:dunno:
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

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    The '205 from a stick will have the 10-spline input shaft; the TH400 versions have the 29-spline. You'll need to change the input shaft on the 205, or change 205's (harder, as the TH400 version '205s are popular for the Doubler crowd.)

    -- A
     
  4. u2slow

    u2slow 1/2 ton status

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    Bore the 205 case, 32-spline input gear, TH400/NP205 adapter, longer front driveshaft, shorter rear driveshaft. Plus whatever shifting mechanism you desire, and a vacuum source.

    IMO give the project some extra thought. The TH400 robs power, and doesn't have the versatile wide-ratio spread of the SM465. Many people (including myself) do the opposite conversion.
     

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