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th-350 to 700r4 conversion, need info please

Discussion in 'The Garage' started by big d, Sep 17, 2004.

  1. big d

    big d 1/2 ton status

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    whats all in it ? what all do i need. was told the 87' up 700's r the best. can i still use my same cross member ? do i need adapters ? any thing else ? whats a good price on a used one ? any and all help is greatly appreciated. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Well this can take a few different paths.

    Are you set on keeping your 203? If you are I can't give much help because I am not sure what it takes to mate a 203 to a th700 besides a different adapter and different output shaft(?). If you can get a complete tranny and t-case that would be better IMHO. The 203 is a crappy case in stock form anyway. The crossmember for a 700/alum case will be needed, TV cable installed and shouldn't be too difficult if you have a Q-jet still. You are correct that the '87 and later 700's are better but if it was me I would take what ever comes by and just have it gone through and built up/updated. You will need to wire up a lock up switch to control the converter on the highway. New drivelines will be needed because of the different lengths of trannies/tcases and style.
     
  3. big d

    big d 1/2 ton status

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    sounds kinda scarey/pricey and alot of work. any one else ? i was hoping for better news, lol. /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/tongue.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/dunno.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif /forums/images/graemlins/yikes.gif
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    rjfguitar is partly correct.
    you need a special outputshaft, the TV cable, lockup wiring, and drivelines.
    you do not need a new adapter as the th350 and 700r4 share the same pattern. the crossmember is also the same. you will have to redrill the frame to move the crossmember back almost 2".

    the th350 is like 1 3/4" or 1 7/8" (can't remember) shorter than the 700r4. so your driveshafts will need to be lengthened/ shortened for that.

    so output shaft is like $100 from AA, TV cable is like $20, lockup wiring oyu can do your self. drivelines shouldn't cost that much to have lengthened/shortened.

    ok now for tranny tech, the 87 and newer 700r4 are alittle better in stock form than the older ones in stock form. after the upgrades, they are preaty much the same strength. if was you, get it rebuilt no matter what, not worth the hassle, besides you have to tear into it to install the outputshaft.
     

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