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Ever wonder how fast your auto tranny can overheat?

Discussion in '1st Gen. Tacomas (1995-2004)' started by AddictedOffroad, Dec 3, 2013.

  1. Dec 3, 2013 at 4:31 PM
    #1
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    I love all the "my A/T Temp light came on" threads.

    So, I decided to show you just how fast an A340 auto tranny in our trucks/4runners can actually overheat.

    Just an FYI, the dummy "A/T Temp" light doesn't come on until the tranny hits 300 degrees. So, when that light comes on, you've already smoked your tranny.

    When the torque converter unlocks in OD, you will see pretty much a one degree per second increase in temp. This is why its so important to run a tranny temp gauge, or Scan Gauge to monitor your temps.

    This video was taken today on flat ground. It was roughly 35* out and I was driving into a stiff 25-30mph wind. You'll notice when the torque converter unlocks because the rpms will jump a few hundred rpms when it happens.

    Here you go:
    http://youtu.be/PlqFwHFHyzI

    Now, the best thing to do when you start hitting temps over 220* is to simply kick the tranny out of OD. When you do this, it locks the torque converter and the temps will drop just as fast as they went up.
     
    Last edited: Dec 3, 2013
  2. Dec 3, 2013 at 4:38 PM
    #2
    StAndrew

    StAndrew Wait for it...

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    Intake, exhaust, lift. Typical stuff.
    How are you reading your transmission temps? Is that through your OBD2 connection?
     
  3. Dec 3, 2013 at 4:40 PM
    #3
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    Yes, Scan Gauge II through OBD II port. But, I have also run tranny temp gauges on previous rigs with identical results.
     
  4. Dec 3, 2013 at 4:42 PM
    #4
    StAndrew

    StAndrew Wait for it...

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    Intake, exhaust, lift. Typical stuff.
    Hmm... My Ultra Gauge doesnt read my transmission temp :mad:.
     
  5. Dec 3, 2013 at 5:47 PM
    #5
    The Driver

    The Driver Trail Runner/Barefoot Beach Runner/Snow Skier

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    Aftermarket tranny cooler, 5100 Series Bilsteins, ToyTec Bilstein front coilovers, SPC UCA's, Alcan leafs, Class 3 Hitch, Tundra Front Brakes,
    Mine won't overheat. I gotz a tranny cooler! ;)

    I installed it along with the tow hitch!
     
  6. Dec 3, 2013 at 6:18 PM
    #6
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    Mine does too. Yes, it will. :D
     
  7. Dec 3, 2013 at 7:41 PM
    #7
    Ridgerunner

    Ridgerunner Well-Known Member

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    Rocklin, Ca.
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    2001 with; cat-back side-swept twin exhaust, elbow mod, Westin bullbar with Hella 450 driving lights, Snugtop XTR camper shell, TRD off-road 2x4-black beauty.
    I appreciate this thread and that informative clip. I will say that when my oldest stepson lived 110 miles from here up in Folsom, Ca. when I'd run up this fairly steep and very long grade on I-80 I could smell that transmission slowbaking. That cooking metal aroma has happened since my truck was new and it still runs perfectly. Very odd how my instincts said "no worry" to such a dramatic burning smell. I would check the fluid afterwards-totally normal with no burnt smell which told me I was smelling the case and its surrounding components as they boiled up near it I guess.
    This is obviously one tough transmission!
     
  8. Dec 4, 2013 at 9:20 AM
    #8
    The Driver

    The Driver Trail Runner/Barefoot Beach Runner/Snow Skier

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    Aftermarket tranny cooler, 5100 Series Bilsteins, ToyTec Bilstein front coilovers, SPC UCA's, Alcan leafs, Class 3 Hitch, Tundra Front Brakes,

    O.K., I'll bite. Would it be possible to hook up that thing to my truck? Now, I'm curious! :eek:
     
  9. Dec 4, 2013 at 9:22 AM
    #9
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    Depends on the year. I believe it will only read 99+ trucks. But, I don't see why not.
     
  10. Dec 4, 2013 at 10:14 AM
    #10
    The Driver

    The Driver Trail Runner/Barefoot Beach Runner/Snow Skier

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    Aftermarket tranny cooler, 5100 Series Bilsteins, ToyTec Bilstein front coilovers, SPC UCA's, Alcan leafs, Class 3 Hitch, Tundra Front Brakes,

    Well since my sig says I gotz a 2002, looks like it'll work. ;)

    I really would like to check this out. Will PM later.
     
  11. Dec 4, 2013 at 10:21 AM
    #11
    Digiratus

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    ScanGauge offers a way to read the trans temp data from the ECU thru the OBDII port. You do have to program the unit with a special xgauge code which is available from ScanGauge.

    http://www.scangauge.com/support/x-gauge/toyota-specific/

    I only have personal experience with my '02 Tacoma and my friends '07 Tundra but have read this will also work with 2ng gen Tacomas.
     
  12. Dec 4, 2013 at 10:24 AM
    #12
    davidpick

    davidpick NWXPDTN

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    xgauge code that digiratus posted works marvelously on my 2004 tacoma. been using it since march or so. :thumbsup:
     
  13. Dec 4, 2013 at 10:35 AM
    #13
    Digiratus

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  14. Apr 19, 2014 at 3:52 PM
    #14
    smmarine

    smmarine Well-Known Member

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    That is trans temp. I'm monitoring mine with my new scanguage. Glad I did, because driving around town for extended trips I'm hitting 215. Gonna be doing a trans cooler install. And a couple things. I believe the scangauge will read the trans temp codes on any a340 series trans with the temp sensor. And when you say lock the trans out of o/d to decrease temp, it does the opposite for me, it increases temp. When I lock o/d up, it decreases
     
    Last edited: Apr 19, 2014
  15. Apr 19, 2014 at 7:42 PM
    #15
    Archer550

    Archer550 Well-Known Member

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    Can someone explain what he means by locking and u locking of the torque converter?
    When does it happen?
     
  16. Apr 19, 2014 at 7:44 PM
    #16
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    When you are cruising down the freeway, and you feel a subtle 500 rpm increase without a downshift. That is the torque converter unlocking.
     
  17. Apr 19, 2014 at 8:02 PM
    #17
    Archer550

    Archer550 Well-Known Member

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    Why does that lead to increaed trans temps so quickly?
     
  18. Apr 19, 2014 at 8:04 PM
    #18
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    Because it allows slipping in the transmission. 99.9% of automatic transmissions do this
     
  19. Apr 19, 2014 at 8:57 PM
    #19
    smmarine

    smmarine Well-Known Member

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    The torque converter also holds most of the heat in the trans. It holds the fluid in till it unlocks, and when it does the temp increases. But I never have the torque converter unlock like that. It licks like that and drops rpm, but it never unlocks and increases 500 rpm
     
  20. Apr 19, 2014 at 9:32 PM
    #20
    AddictedOffroad

    AddictedOffroad [OP] Well-Known Member

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    No. It creates more heat when it unlocks. And yes, it does jump 500rpms when it unlocks.

    Run on a slight incline into a headwind, and it will unlock. Tow with it, it will unlock in OD.

    Next time your driving it, tap the brake with your left foot at speed for a sec. What you will feel is the torque converter unlocking. Take a look at how high your rpms jump.
     

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