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Do I need Trans work with a big motor?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Hustler, Jun 13, 2001.

  1. Hustler

    Hustler 1/2 ton status

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    I have a 90 Jimmy and the 700R just said bye bye. I was planning on rebuild the motor, and now that I need to pull the Transmission out, I am doing it all. My question is I am going to build and put a 383ci stroker back in and since I have to rebuild the transmission, what do I need to do to keep the 700R from beaking. I don't want to put a 350 or 400 trans in, I like the overdrive since I will be using this to tow my race car. Tell me what you guys think is the best thing to do. Thanks.
     
  2. Ryeguy

    Ryeguy 1/2 ton status

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    Lots of good articles on the 'net and in magazines for how to build the 700R4 to handle the torque of a 383. Won't be too hard. Lots of companies that will sell you all the hard parts that you need as a kit too. You shouldn't need to go to a TH350 or TH400 to handle a 383. Now if you were going big block that'd be a different story... (go big block!)

    --Rob
     
  3. HarryH3

    HarryH3 1 ton status Author

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    GM doesn't recommend that you tow with a 700R4 in overdrive. They say to leave it in Drive for towing. [​IMG] Not sure what the aftermarket builders have to say on the subject.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <A target="_blank" HREF=http://www.angelfire.com/super/ThunderTruck>http://www.angelfire.com/super/ThunderTruck</A>
    It's a great day to be alive...
     
  4. '73 K5

    '73 K5 1/2 ton status

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    Yea, I wouldn't use the overdrive for towing either. Go for a 400.

    '73 K5
    Chevy good...Ford bad
     
  5. Hustler

    Hustler 1/2 ton status

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    Ryeguy,
    I would like to go with a big block, but the only big blocks i have are for my 1/4 drag car. I don't really want to put a 1000 hp big block in to drive all the time. It would be fun though. I picked the 383 because that is what I used in my Late model stock car and I have 3 of them in my shop. I think the motor will be about 450 to 500 hp. I don't know what I can get out of it and still be able to pass emissions. I just don't know anything about the 700R trans and don't know what kind of power it can take without breaking. I thought you could tow with the 700R if you installed a trans cooler. Thanks for the replys though guys.

    <P ID="edit"><FONT SIZE=-1>Edited by Hustler on 06/14/01 10:55 AM (server time).</FONT></P>
     
  6. Ryeguy

    Ryeguy 1/2 ton status

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    Wow! Cool!

    You may be pushing the envelope of reliability out of that TH700R4 with such a strong 383. The 700R4 can be built strong, but it's going into a heavy truck that you're towing with. A few phone calls to the "big guys" who build these transmissions may be in order. I've got a mild big block (~400hp, 500-550tq) and I was told to forget about the TH700R4 living behind it.

    --Rob
     
  7. Hustler

    Hustler 1/2 ton status

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    I may have to make a few calls myself. I might want to get a th400 and put it in the place of the 700R. If it can't work behind 400hp, I am in trouble. I know I will have that much power or more.
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    A lot of 700's don't live behind 210 hp and stock tires with no towing...they just don't hold up well in a heavy truck. A lot of the rebuilds out there actually cause premature failure as well. The corvette servo in an otherwise non corvette 700 is a prime example of a mod that seems good but will actually kill the tranny fast.

    Get a built TH350 or 400.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
     
  9. bigk

    bigk 1/2 ton status

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    4Wheel Parts Wholesalers advertises 700's and 4L80's built for serious torque.
     
  10. HarryH3

    HarryH3 1 ton status Author

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    Take a look at my post again. GM recommends that you don't tow with the 700R4 in Overdrive. It's OK to tow with it in Drive with a really big tranny fluid cooler. So you have the overdrive, but don't use it when you need it most. [​IMG]

    Will a 700R4 live behind your engine? Probably not for long. GM put Turbo 400's in the 3/4-ton Suburbans up through at least '91 to deal with towing heavy loads. The 700R4 just wasn't up to the task.

    <font color=black>HarryH3 - '75 K5</font color=black>
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    It's a great day to be alive...
     

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