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Let’s talk transmission temps

Discussion in 'Engine & Drivetrain' started by BH1989, Mar 8, 2021.

  1. 67RS427

    67RS427 Full Access Member

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    I figured I would chime in here since you guys were getting in a pissing match over the electric fans... @03_GMC is 100% correct and everyone else arguing with him is wrong. On these trucks, at least with the E38 controller, the electric fans are only triggered on or off based on ECT and AC pressure. See the pic attached from HP Tuners. There is literally NO handles to turn the fans on or off based on MPH. Discussion over...

    Screen Shot 2021-04-16 at 4.41.09 PM.png
     
  2. 03_GMC

    03_GMC Full Access Member

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    Yes thank you! All this time I wish I would have gotten this picture when the truck got tuned!


    Sent from my iPhone using Tapatalk
     
  3. Foggy

    Foggy Full Access Member

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    Well, I'll be a monkey's uncle... I was informed by a couple of tuners that
    the fans would not come on at hwy speeds... In OEM form...
    Due to the air pressure the fans would do no good at speed....
    My coolant temp never got above 220* towing, so I guess that's why..
    My trans temp did hit 225* towing and thats my concern....
    It should not run hot at all with my cooling set up...So I'm going to change
    the tune and trans tune now that I have my derale trans cooler remote mounted
    and my snow performance meth injection installed
     
  4. Bill 1960

    Bill 1960 Full Access Member

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    Firstly, let me say I don’t really know specifically how GM coded the fans. What I HAVE done is coded a few machines myself, plus I have used HPTuners. Machine code can use both fixed values and variables in calculation.

    HPT is not a tool for recoding the engine, it’s not even capable of showing you the code (at least not the last version I used). HPT is a tool for editing the variables used in various powertrain algorithms.

    All of which is a long winded explanation of why the lack of a modifiable variable in HPT does not tell us anything definitive regarding the algorithm, and what other factors may or may not be included in that algorithm.
     
  5. BG1988

    BG1988 Full Access Member

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    in the summer the 2mode rarely gets over 165F even when it was 110F outside in the winter it barely warms up to 145F( mostly because the fans are off while driving) I highly recommend cleaning it gently with a tooth bush and get the dead insects off of the radiator you can bet cleaning off a few can make a huge difference
     
    Last edited: Apr 18, 2021
  6. Foggy

    Foggy Full Access Member

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    Pics I promised [​IMG][​IMG][​IMG][​IMG]

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  7. Foggy

    Foggy Full Access Member

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    I had not done the wiring yet as of these pics.. I grounded the fan directly to
    the round frame bar that holds the splash shield. I replaced one of the top bolts
    with a stud and used 2 nuts .. It grounds just fine...
    The positive wire is ran into the cab to a switch, then to acces power. So
    I can manually turn it on when needed. I didn't use the inline thermostat switch
    that came with the derale kit.
    I removed the OEM aux trans cooler and spliced into the lines.. Thats why
    they are marked .. the blue is the return to the trans - the coldest !

    It has not been hot here yet and I haven't towed yet... but I did drive it around
    my suburbs and got the trans temp to 165*.. I turned on the fan at it dropped
    down about 20* so I know it works.
     
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  8. BG1988

    BG1988 Full Access Member

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    have you thought about adding an AUX manually controlled fan for the transmission cooler?? i recommend running at under 165-170F this will make the transmission last WAY longer then intended by the manufacture...


    145F is typical for me on the M99 transmission. Allison transmission? (Beefed up 6 speed 4L60E ??).. i heard some people claim it can handle upwards of "750 Ft-bl of torque" 6.6 Duramax was going to be offered as an option on the hybrid.. most likely it would have been a downclocked 250BHP version. YES i would have gotten a dirtymax version



    Note: I don't see an AUX cooler on mine




    and some people have reported blowing up crankshafts too(literally breaking them) or exploding the input/output shaft on the transmission on startup...
     
    Last edited: Apr 21, 2021

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