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700R4 to T400, who's done it and what else must be done?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by PetaKane, Sep 15, 2002.

  1. PetaKane

    PetaKane 1/2 ton status

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    700R4 to T400, who\'s done it and what else must be done?

    It will bolt up with a 208 case, right? And I'll need a longer rear shaft and have to move the crossmember, right?
     
  2. HarryH3

    HarryH3 1 ton status Author

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    You'll need a different adapter to mate the 208 up with the Turbo 400. The 700R4 has a 27 spline output shaft and a square, 4-bolt pattern at the tail end of the housing. The Turbo 400 has a 32 spline output shaft and a hexagonal, 6-bolt pattern at the tail end of the housing. But the mid-80's 3/4-ton Suburbans came the the 400/208 combo, so you should be able to find the right adapter in a yard. 3/4-ton pickups are probably a suitable donor also.
     
  3. ken

    ken 1/2 ton status

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    HarryH3 is correct. Additionally, you will not have to move the crossmember or modify driveshafts, because the T400 is close enough ;to the same length as the T700. I know, I did this very conversion in my wife's '90 Suburban. Got rid of the POS t-700 after rebuilding it SIX times. T400 should last FOREVER now.
     
  4. chillywilly

    chillywilly Registered Member

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    Did mine a few years ago...spent $4 or 500 with advanced adapters.Very complete kit if ya aint got time for lookin.
     
  5. BurbLover

    BurbLover 1/2 ton status

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    Glad to see this post. I picked up a TH400 last month with a 208 attached for $500. Both rebuilt about 1500-2000 miles ago. Anyway, Once I get my engine rebuilt, I plan on swapping the tranny, unless of course I find a buyer for the tranny first. I'm actually thinking of keeping my 208 which is attached to the 700 as a spare, especially since I picked it up rebuilt about 15K miles ago.
     
  6. MNorby

    MNorby 3/4 ton status Premium Member GMOTM Winner

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    After toasting my 4th 700/208 I picked up a 400/241 form a 90 burban and eveything builted right up. Only diff is the detent cable on teh 700 and the vacuum line on the 400 but that is nothing really /forums/images/icons/cool.gif
     
  7. Calclips

    Calclips 1/2 ton status

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    Re: 700R4 to T400, who\'s done it and what else must be done?

    You'll have to wire a kickdown switch to go behind your gas pedal for the T400 kickdown. Your 700 uses a TV cable to hooks up to the carb (or throttle body if you have it).
     

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