Let’s talk transmission temps

[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!


Sent from my iPhone using Tapatalk

 

[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...