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400/205 conversion

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by wayne, Aug 23, 2001.

  1. wayne

    wayne 3/4 ton status

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    I am converting from a 700r4/241 to a 400/205 and just need to know how much of a PITA it is going to be and what to expect to run into in doing the swap.

    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  2. HarryH3

    HarryH3 1 ton status Author

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    I swapped mine from a 350/203 to a 400/205 many years ago. You'll need to move the crossmember, this means just drilling 4 new holes in the frame. I got mine with the 400/205 crossmember, so I'm not sure if things will bolt to the 700R4/241 crossmember.

    You'll need switched power to the kickdown switch that has to be mounted to the gad pedal bracket. I got the switch for mine from an old Jeep Wagoneer. They came with Turbo 400's for many years.

    You'll need to run manifold vacuum to the modulator on the tranny.

    The shifter for the 205 may present a challenge. Mine has the shifter mounted to the t-case and it needs a big hole in the floor to have room to shift, move around, etc. The shifter for the 241 is bolted to the floor, so you'll probably have to break out the Sawzall there. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  3. californiak5

    californiak5 1/2 ton status

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    Is the power for the kick down connected to the male fitting that is on the opisit side of the tranny than the vacuum mod? I was wondering what that was there for on the tranny I have. Thanks in advance for your help.

    See Ya,
    Keith

    [​IMG] <font color=green>Born to Drive My K5</font color=green> [​IMG]

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  4. HarryH3

    HarryH3 1 ton status Author

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    That sounds like it. [​IMG] When 12 volts is applied to that input, the tranny goes into passing gear mode. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  5. wayne

    wayne 3/4 ton status

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    I am pulling everything out or a Burb that has the donar trans and t-case. Will it have everything I need for the kickdown? I assume it will.

    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  6. HarryH3

    HarryH3 1 ton status Author

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    Yep, crawl under the dash and look at the bracket that holds the gas pedal. You'll see an electrical switch near the top that gets engaged when you romp the loud pedal. Take that switch and the wiring with you. That's what make the kickdown happen. [​IMG] My '75 had the holes in the gas pedal bracket for the switch to attach to. Just screwed it into place and wired it up.

    <font color=black>HarryH3 - '75 K5</font color=black>
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  7. wayne

    wayne 3/4 ton status

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    Mine is an 89 so do you think I will need the to swap the pedal assembly? Thanks Harry.

    <font color=blue>Wayne<font color=blue>
    <font color=blue>Happy Trails<font color=blue>
     
  8. HarryH3

    HarryH3 1 ton status Author

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    No idea on that. I'd bet though that since the Turbo 400 was still available in '89 Suburbans that the '89 K5 had the same bracket and that it has the holes drilled in it. GM is the king of making parts universal! [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
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