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TH 350 to 700r4

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Sparky, Sep 27, 2000.

  1. Sparky

    Sparky 1/2 ton status

    Aug 20, 2000
    Likes Received:
    San Antonio(summer) Texas A and M (school year)
    Now I know what you are all going to say. Why swap for the weaker 700 huh? I'll tell you why, i want 4.10's and those dont go well with a 3 speed.

    Now that I got that out of the way, i will get to the point. How hard is it to swap the two? Right now I have 350?th350/np203. The 3 speed and full time four wheel drive hinder the on road performance, and the 700r4 will help the off and on road performance so what could be better than that.

    I guess mr real question is... What all is involved (adapters for the 203, computer stuff, etc.) Oh, and where would you suggest I get that 700r4 rebuilt so it is transformed from its factory state as a boat anchor to a real transmission. I know they can be bullet proof with the right internals. Thanks for any help.


    78 K-5
  2. k5king

    k5king 1/2 ton status

    Jul 23, 2000
    Likes Received:
    Parkesburg, Pennsylvania
    well sparky, i went the completely opposite way your going! i had a 700r4 and destroyed it so i put in a th350 w/ a 205 case on it. i think that to run th700 on a 203 you'll need to have the shafts from your th350 installed in your 700 for one they're stronger and two the grooving is different on both. you will probably need an adapter plate also and you will definately have to get your driveshafts replaced!!!!! there is about 4"s of defference between the two setups. if you want to buy a good tranny you can get them from TCI trans. or maybe B+M. hope this helps. oh yeah you will need to get a different shifter!!

  3. KrebsATM02

    KrebsATM02 1/2 ton status

    Mar 21, 2000
    Likes Received:
    College Station, Texas
    Hey, I just got done with replacing my 700r4. It was a lot easier than i thought it would be. I looked at alot of transmissions before i ended up with this one. This one is called the "Raptor", kinda stupid name i know but it really had some bad ass parts in it. Here is the web adress for the place that makes them http://www.transmissioncenter.net/highperflist.htm
    I am really satisfied with it so far. It shifts hard if you have the pedal on the floor and shifts nice if you don't have alot of power going to it. The one thing i really like is its holding power in overdrive. I used to have 31's and when i was going up hill, it would shift if i barely applied the gas to it. Now i have 35's and 4.10's and going up hill i actually have to put my foot on the floor to make it shift. It doesn't like to shift out of overdrive once it's in and i like that cause i get some serious gas mileage now. If you want to know more just email me dkrebs@neo.tamu.edu later doug

    Doug Krebs
  4. You can't use the shaft out of your 350 in a 700r4.You will have to buy one from advance adapters,they also have a table in there catalog showing what fits and what they can adapt to.The 700r4 and the 350 have the same style houseing at the output all you have to do is have the special shaft installed in the 700r4.There are several ways to make the lock up work,there have been many ideas on this awhile back
    so just do a serch on this subject.
    Good luck


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