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700R4 Heat Problems?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Monster, Sep 30, 2002.

  1. Monster

    Monster Registered Member

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    I just had my 700R4 rebuilt and beefed up which costed 1800 bucks!!!!! Everyone says heat is what kills this tranny. The Trans shop told me I had 3.07 in my rear and I had to change them if i wanted the trans to last. Before i changed the gears I installed a trans temp gauge to see what the temp was. When I drove around town it would hit 210 no problem.(I have the sending unit for the gauge in the line going to the trans cooler) I had the gears changed to 4.56 and the temp stays between 175 to 185 in town. For the first time i took it out on the highway and she hit 210 again. I do not like this. Any one have a idea why it gets so hot on the highway. Also does anyone else have this problem. I Do Not want to spend that kind of cash again.

    1986 K5,Np-208,35 BFG,300 Horses under the hood.
     
  2. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    You haven't specified if you're running an auxilliary tranny cooler along with your stock one. Are you?
     
  3. Monster

    Monster Registered Member

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    yes i run a auxilliary tranny cooler . Including the stock,i run two other ones. which makes 3
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I've been curious for quite some time as to how much of a restriction, if any, adding coolers to the tranny lines is.

    If you think about it, the cooler HAS to slow the fluid down some, wonder with your 3 coolers if thats what is going on. Besides, with 3 coolers, you must have quite a few bends in the system, which will also slow things down. You want it moving through as fast as possible.
     
  5. imiceman44

    imiceman44 1 ton status

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    Slowing down the coolant is sometimes what you want, it'll give it time in the cooler to cool down. The problem lies in the original cooler.
    Keep the other 2 and eliminate the one in the radiator, it is geting the heat from the engine coolant, 210 is normal for a low geared rig on the highway.
    I know because I had the same problem in my Jeep.
    Also on the other end, I had a van with 2.73 gears and 31" tires, and it over heated going up steep hills, it was the tranny heating up the engine, wehn I cooled down the tranny with a seperate cooler, the engine was fine.
    Just my experience, hope that helps.
    IceMan
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    You don't want fluid slowing down. You are air cooling this stuff, (except the in radiator stock one, which is kind of both) and the longer you keep it in the radiator, the worse the heat transfer. Get it in, get it out, and make sure airflow is good.

    Same applies to the engine cooling system, except they have a thermostat that closes if temp gets too cold.
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Just an FYI- When you bypass the factory cooler, your ATF takes longer to warm up in cooler weather. You also risk damaging your tranny from OVERcooling......

    Every aftermarket cooler manufacturer recommends running the factory cooler along with their product.
     
  8. Monster

    Monster Registered Member

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    I guess everyone has there own opinion on how to cool a transmission properly and what the temp should be /forums/images/icons/grin.gif .I dont drive on the highway to much so I am not going to worry about it. My trans temp stays at 180 around town so Im happy. /forums/images/icons/laugh.gif

    /forums/images/icons/tongue.gif Thanks /forums/images/icons/laugh.gif
     
  9. imiceman44

    imiceman44 1 ton status

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    Well I could agree with your logic, but after reading the instruction on my flexalite cooler that gives you 2 options inline w/ the original or standalone, I decided to go with standalone.
    I do a lot of research before I ever do anything and I analyse it to death, then I proceed with caution, making tests and checking everything every day, I log everything and that gives me a basis for experience.
    I am an Architect, and a fabricator, and I need the knowledge to be able to create efficiently, so I always start with the experts opinions and then the manufacturers and then build on that.
    But then again, I have seen some people do there own thing and it works.
    As long as it works.
    By the way, it's always good to have guages and monitor everything whenever you make modifications so you know if you are doing good or bad.
    Inever had a problem getting the tranny fluid up to operating temp, and never got too hot.
    Sorry for the long message.
    IceMan
     
  10. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I notice from your bio that you live in CA. I agree that you should be able to run an aux. tranny cooler by itself in warm weather. I don't believe I said otherwise....

    However, where I live, a guy who runs the aux. cooler by itself risks damaging his tranny during the winter. Not only that, without the stock cooler/warmer, your ATF would NEVER warm up prior to driving. That's why I mentioned "cooler conditions" in my previous post. You warm weather guys always forget that some of us have REAL winters..... /forums/images/icons/wink.gif /forums/images/icons/laugh.gif
     
  11. GRINCH

    GRINCH 1/2 ton status

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    I will vouch for Canmore!!! I too live in the frigid cold. My cooler (B&M) has a bypass so when it's cold it doesn't run through the cooler. I run it through my stock cooler and then to the B&M. I came over a pass the other night and when I got to the top I was at 180 then when I hit the bottom I cooled all the way down to 120.
     
  12. imiceman44

    imiceman44 1 ton status

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    Yeah sorry, I never think of that much, all my life I lived in warmer weather, I never even used antifreeze in my coolant, just rust inhibitors and additives to soften the seals, until I came to Sacramento where you sometimes do get freezing temps, and I sometimes go on snow runs, but that is with my manual truck not the auto. And it has an electric fan for the radiator not the direct drive.
    You are right, that is like driving without a thermostat, you could break an engine going down after a hard pull up a hill.
    You are on top of thing guys, keep watching, and don't hesitate to corect me, no body is perfect and that's why we meet here, and learn from each other.
    /forums/images/graemlins/smile.gif
    IceMan
     
  13. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Any time, brother!!! /forums/images/graemlins/wink.gif

    I wish I lived somewhere where it never froze. Heck, we got a couple of inches of snow today!!! /forums/images/graemlins/eek.gif Oh well, my view of the mountains is nice. /forums/images/graemlins/tongue.gif
     

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