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turbo 400

Discussion in 'OffRoad Design' started by jayoshow, Nov 27, 2005.

  1. jayoshow

    jayoshow Newbie

    Nov 19, 2005
    Likes Received:
    Beaverton, Oregon
    Hey , I have a 1970 chev half ton with the 350 turbo, 205 t case I,m going to install the turbo 400 with the 205, oh the truck has 350 sbc. My question is with the longer t 400 will Ineed to move engine, tranny , t case forward so the 205 shift levers do not hit the seat? I know these trucks came factory with t 400,s. Right now the truck is down to frame with axels only. Thanks
    Last edited: Nov 28, 2005
  2. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Nov 28, 2000
    Likes Received:
    Western Massachusetts

    You "could" move everything forward just to line up the shifter...................
    but then you run into fan/radiator clearance issues, custom fabing mounts, etc, etc.

    Your current 205 will not work as it is a male 27 spline and the TH400 version of the 205 is 32 spline female. There is also two different versions of the TH400 version NP205. A figure 8 style with tall adapter and a 6 bolt circular style with short adapter. Both styles use a different crossmember, adapter, mounts, and shifter/linkage.

    Your best bet (if you haven't already) is locate a TH400 NP205 that has the adapter, crossmember, linkage, shifter, etc. and it should be a bolt in affair (may have to drill new holes in the frame for the crossmember....but they might already be there if you are lucky). The shifters were designed for each setup, so if you get the case with the proper adapter, shifter, linkage everything will line up with the hole in the floor.

    You will also have no kickdown with the TH400 unless you hook one up to the throttle pedal (again see if you can get it from a donor). Even if you don't, you can still downshift manually. And remember to hook up the vacuum modulator line. I believe the cooler lines can be re-used if tweaked (somebody correct me if this is wrong).

    I can't remember what the length is on a TH350/NP205 and the length on either version of the TH400/NP205 combo's, but it MAY cause driveshaft length issues. I have done several conversions but not this one, so someone can probably shed more light onb this detail.
  3. Stephen

    Stephen 1/2 ton status Moderator Vendor

    Sep 15, 2000
    Likes Received:
    Carbondale Colorado
    The factory shifters and our shifters have a big bigger offset built into the handles to move them forward so they hit the hole in the floor, so that probably won't be a problem.
    Take a look at our sale, we have our TH400/NP205 adapter kits on sale......

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