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TH400/205 swap anyone done this??

Discussion in 'The Garage' started by MTBLAZER89, May 21, 2003.

  1. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    I want to swap out my 700/241 for a 400/205. Has anybody done this how much "extra" work is involved?? It is an 89 K5. 400/205 coming out of 78 K30. Thanks

    -Brian
     
  2. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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  3. AnthonyG

    AnthonyG 1/2 ton status

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    I swaped a 700/208 out for th400/208 and it was a brease
    The only thing you will hae to worrie about is a rear driveline the xmember, tcase shifter, and inspection cover out of the k30 but other than that it should be easy
     
  4. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    Both of your driveshafts will need to be modified and you will need the t-case shifter. You'll need to find a cross member out of a pre-85 1/2 or 3/4 ton truck/Blazer/Sub (flat style), the one out of the K30 wont work on your frame. You will have to redrill the frame for the cross member because it will move about 3"~4" further back.

    Your tranny shifter will connect/work the same, as well as, your speedo cable.
     
  5. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    OK update the donor truck is a 78 K20 not a K30 /forums/images/graemlins/angryfire.gif. Can I use the front driveshaft out of the truck? Can I use the crossmember out of the truck? Thanks everybody.

    -Brian
     
  6. u2slow

    u2slow 1/2 ton status

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    The crossmember will be necessary, since the 78 th400/np205 adapter is much taller (hangs lower) than the th700/np241 adapter.

    Driveshaft should work too.... its the tranny, t-case and front axle (and of course lift) that decide the length. If this 78 has a 10-bolt front it should be the *exact* right one. If it has the D44... well it might be a little off.

    Maybe double-check what you're getting. A 78 3/4-ton with a TH400 should have an np203 behind it. Of course people swap things around, so anythings possible.
     
  7. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    Do they make an adaptor for the 400/241 combo??
     
  8. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    I believe that combo was available in a 3/4 ton Sub in 89/90.
     
  9. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    so my 241 will bolt up to a th400???
     
  10. nvrenuf

    nvrenuf NONE shall pass! Premium Member

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    No, your 241's input shaft should be 27 spline - to bolt it to a 400 you will need a 32 spline input. I'm sure the inputs could be swapped but I don't know what's involved or how hard it is to get the parts.
     
  11. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    anybody else?? /forums/images/graemlins/1zhelp.gif kinda leaning towards the 400/241 combo if it is possible I like the low range. Or the 208 if that is an easier swap??
     

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