Let’s talk transmission temps

[03_GMC]

I really really really don't like to argue with anyone on the internet.. I'm too old...
But I want people to know the facts>>>>>
Your electric engine cooling fans will NOT be commanded to turn on NO MATTER what
the coolant temp is at highway speeds...
Maybe you have a custom tune that does command them to ON at 60mph,
but it really wouldn't have any benefit due to the incoming air at speed anyway.
This is the reason the OEMS do not do it.
IF yours turn on at 60mph, then you have the unicorn... I do understand the differences in mechanical, electrical, viscous types of fans that the oems have used
for over 100 years

I do not have any "swap" crap in my rig. It's the factory engine, trans, diffs, etc/
I do have a supercharger and a tune of course.
My fans are programmed to come on low speed at 202* and high speed at 212* ..
I can watch my duty % at all times so I know exactly when the fans operate.
But as stated, oem electric fans don't come on at 60mph..Now, if you slow down then
they do come on and will run on high if temp demands it. But keeping cool at a steady
60-70 mph while towing on grades in 90*+ weather presents a whole different set
of parameters

Hey Foggy I’m not trying to argue either. I also wasn’t implying you had a crappy swap. Hearing that you had an intercooler and were doing a meth injection setup from snow performance naturally makes most people assume you have a diesel. So I am sorry if that assumption upset you that wasn’t my intention. I understand the logic behind going at highway speeds and that air is naturally moving through the radiators at a higher speed than when on the side roads at 30-40mph. However the engineers have designed these fans to move air at a faster rate when set to a 97% duty cycle than the air is moving going highway speeds with no fan helping to pull the air through. GM doesn’t allow the fans to go to 97% duty cycle until your coolant is over 225. Whether you are on the interstate or not. Once you hit that coolant temp the fans then run at max and can finally help cool the engine down. The factory ECU cooling fan duty cycles are set by coolant temp not speed. I watched the tuner change it in HPTuners. Again not trying to argue with you as you seem very smart and knowledgeable. I am just sharing what I have seen with my own eyes and know from asking many questions during the tuning process. A replacement ext tranny cooler is a must. The factory one is junk. However the tune also helps keep your vehicle from getting as hot as quickly as it does with the factory parameters. I think both are a great upgrade and a must when towing with these trucks.


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[03_GMC]

I really really really don't like to argue with anyone on the internet.. I'm too old...
But I want people to know the facts>>>>>
Your electric engine cooling fans will NOT be commanded to turn on NO MATTER what
the coolant temp is at highway speeds...
Maybe you have a custom tune that does command them to ON at 60mph,
but it really wouldn't have any benefit due to the incoming air at speed anyway.
This is the reason the OEMS do not do it.
IF yours turn on at 60mph, then you have the unicorn... I do understand the differences in mechanical, electrical, viscous types of fans that the oems have used
for over 100 years

I do not have any "swap" crap in my rig. It's the factory engine, trans, diffs, etc/
I do have a supercharger and a tune of course.
My fans are programmed to come on low speed at 202* and high speed at 212* ..
I can watch my duty % at all times so I know exactly when the fans operate.
But as stated, oem electric fans don't come on at 60mph..Now, if you slow down then
they do come on and will run on high if temp demands it. But keeping cool at a steady
60-70 mph while towing on grades in 90*+ weather presents a whole different set
of parameters

Hey Foggy I’m not trying to argue either. I also wasn’t implying you had a crappy swap. Hearing that you had an intercooler and were doing a meth injection setup from snow performance naturally makes most people assume you have a diesel. So I am sorry if that assumption upset you that wasn’t my intention. I understand the logic behind going at highway speeds and that air is naturally moving through the radiators at a higher speed than when on the side roads at 30-40mph. However the engineers have designed these fans to move air at a faster rate when set to a 97% duty cycle than the air is moving going highway speeds with no fan helping to pull the air through. GM doesn’t allow the fans to go to 97% duty cycle until your coolant is over 225. Whether you are on the interstate or not. Once you hit that coolant temp the fans then run at max and can finally help cool the engine down. The factory ECU cooling fan duty cycles are set by coolant temp not speed. I watched the tuner change it in HPTuners. Again not trying to argue with you as you seem very smart and knowledgeable. I am just sharing what I have seen with my own eyes and know from asking many questions during the tuning process. A replacement ext tranny cooler is a must. The factory one is junk. However the tune also helps keep your vehicle from getting as hot as quickly as it does with the factory parameters. I think both are a great upgrade and a must when towing with these trucks.


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[Rocket Man]

The only way the fans will be on at highway speeds is if you’ve done some crazy programming in the tune which is pointless because your electric fans will actually be hindering airflow at that point. The factory tune turns them off at a certain speed, not sure but I believe it’s 40-45 and they free spin at that point. This also conserves fuel since you don’t need the alternator loaded with 50 amps of draw or whatever they pull. I know it’s a lot. I’m with with @Foggy on this. I don’t know what tuner told you the fans run at highway speed. I know mine don’t.

 

[Rocket Man]

Also, an intercooler is standard with a blower like I also have, and meth injection is used on gas just as much as diesel. I have considered it on mine. So most people -especially here- here don’t assume it’s a diesel when talking about these.

 

[03_GMC]

Also, an intercooler is standard with a blower like I also have, and meth injection is used on gas just as much as diesel. I have considered it on mine. So most people -especially here- here don’t assume it’s a diesel when talking about these.

I honestly didn’t even think about a blower until he said something. But I definitely know that it’s wise to run one. Once the coolant temp hits a certain degrees your fans will kick on. If you’ve ever gotten hot going down the interstate you’ll hear the fans run at full speed. That’s when my temps would finally start coming down. I don’t disagree that they may shut off but if your coolant temp gets to the point of needing the full duty cycle of the fan then they will turn on no matter the speed.


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[Rocket Man]

I disagree. And I’ll leave it at that. BTW most of the blower kits out there include an intercooler as part of the package. My Whipple did.
Edit: I stand corrected. After I looked into it, it seems the fans may indeed turn on in an overheat event on the freeway. This will now require me to look into this further. I have never experienced this though.

 

[03_GMC]

I disagree. And I’ll leave it at that. BTW most of the blower kits out there include an intercooler as part of the package. My Whipple did.
Edit: I stand corrected. After I looked into it, it seems the fans may indeed turn on in an overheat event on the freeway. This will now require me to look into this further. I have never experienced this though.

All good man. Just like you I am here to help out. I saw and experienced an issue and was able to get a part of a solution and wanted to share.


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[Geotrash]

This confirms what I experienced as well. As I was approaching the peak temps during a few hill climbs, I could feel something electrical engage, and the coolant temp would come down 10º-15º on its own, while still running hard in the climb.

 

[Foggy]

I'll get a couple of pics of the install in next day or two with the derale
installed behind the front bumper

 

[03_GMC]

I'll get a couple of pics of the install in next day or two with the derale
installed behind the front bumper

Awesome man. Looking forward to seeing it!


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[67RS427]

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...

 

[03_GMC]

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...

View attachment 276619

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


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[Foggy]

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

 

[Bill 1960]

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.

 

[BG1988]

I’ve been watching mine closely, both the original trans and my just installed GM reman run in the 190’s and sometimes over 200. This just driving around town. Of course with the 35’s it’s somewhat like trailer towing continuously.

My plan has been to add the OEM air cooler because I hate aftermarket trans coolers with hose barbs and rubber hoses. I’ve seen far too many leaks.

Thanks to @Geotrash for sharing those pictures. Seeing the Trucool 40 with hard lines has given me another option to consider.

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

 

[Foggy]

Pics I promised [emoji3526]

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[Foggy]

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.

 

[BG1988]

Unfortunately, Even With a Tune... Highway towing temps won't be affected.
The fans don't (and won't and shouldn't) operate above a certain MPH..about 40 mph

So when towing at highway speeds, the fan settings don't mean a thing at all

Thats' the reason why many of us that tow have explored better cooling options
such as better radiators and external trans coolers.

Yes, around town, having the fans set in conjunction with a lower thermostat
temp will help... but not on the highway

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...