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Swap in a TH400 in place of a 700R4?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 87superblaze, Jan 22, 2002.

  1. 87superblaze

    87superblaze 1/2 ton status

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    Is it possible to swap in a TH400 in place of a 700R4. I have an 87 with 350>700R4>241 T-case. What will I need? Do I even need the strength of a TH400. Mine is already modified but I like the idea of having the strength when I need it. I tow heavy rigs with the blazer and some day I would like to upgrade to a 383. Any comments?


    My Truck <a target="_blank" href=http://www.community.webshots.com/user/nicksm79>http://www.community.webshots.com/user/nicksm79</a>
     
  2. dawson444

    dawson444 1/2 ton status

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    It will work. I swapped my 700/208 out this weekend for a TH400/203. I almost got it running.

    Dawson
    Raleigh, NC

    88 K5, 6" lift, 36" TSL Radials, 14 Bolt, Rancho 9012s
     
  3. Effyoo

    Effyoo Registered Member

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    This has been covered here before. If you check the archives, you can probably find anything you need to know. In short, yes you can, but the 700 has a great 1st gear and can be built to handle just about anything you're going to be throwing at it. The 400's (numerically) low first gear, coupled with whatever gears you have in the diffs, may keep your trucks operating RPM where it isnt efficient. Anyone who refuses to stick with the 700 because it can't be built tough is wrong and overdriveless. &lt;---New word :)

    "There are 3 kinds of people in this world...Those who can count, and those who can't"
     
  4. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    True it can be built to handle almost anything, but even a cheap rebuilt 400 is very tough/durable. At much less cost then a properly built 700R4.
    *
    *
    (1500-2000)-TH-700R4
    (500-600)-TH-400

    This is what they go for during a high perf rebuild.

    But to the original poster, try searching the archives, there is a ton of info there. But off the top of my head, the driveshafts will likely need shortening/lengthening. Also you will need the proper adapter. The X-member may need to be moved. You will need an electric kickdown switch for the 400. You will need to work out the shifter(s)...

    You are prob better off buying a Raptor tranny.. $1500 with stall convertor of your choice. It will handle something like 600ft/lbs. That is unless you just really want a 400. I have a 400 and I like it. I swapped from a 465. But each his own.

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Don't forget the 700R4 is 27 spline and the TH400 is 32 spline so the T-case won't just bolt up.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  6. ftn96

    ftn96 1/2 ton status

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    Like Rene said, you'd have to dis-assemble the 400 all the way down so you could replace the output shaft to match your 241 and you'd need a "special"-ly priced adapter to make the bolt patterns match up. May be better off to find a matched combo like dawson found and replace the whole kitten ka-bootal and then only have to worry about the actually functionallity issues such as shift points and so forth.

    Still trying to figure out why they have brail on drive thru ATM's?? [​IMG]
    <a target="_blank" href=http://www.mccords.s5.com/myk5/index.htm>NashvilleK5</a>
     
  7. 83ZZ502_Jimmy

    83ZZ502_Jimmy 1/2 ton status

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    Yeah I knew that but had a brain fart. I just had to forget something [​IMG]

    John

    <font color=blue>"When all else fails, read the instructions, or get a bigger hammer"</font color=blue>
     
  8. 87superblaze

    87superblaze 1/2 ton status

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    Thanks for the info. It sounds like I would be better off with my 700R4. I just keep hearing horror stories about 700's letting loose all the time.

    Sorry I had to post again but if you search for TH400, there's like a zillion different things that come up.

    My Truck <a target="_blank" href=http://www.community.webshots.com/user/nicksm79>http://www.community.webshots.com/user/nicksm79</a>
     

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