Let’s talk transmission temps

[thompsoj22]

View attachment 272912

I remember this pic, YIKES! It is what encouraged me to get the trans cooler installed. I know LS engines like/need to rev and lugging them is the worst thing you can do while towing but this pic is "juevos grande" territory! You were climbing over vail co. right?

 

[thompsoj22]

This was truly THE worst case. Running the Ike Gauntlet, at 16,300 lbs. Silverthorne to the Eisenhower Tunnel, cresting at over 11,000 feet in altitude.

I just like sharing this pic to make heads explode. Original trans, 207k miles, 30k at max GCWR. Stock coolers.

tik toc tik toc tik toc tic tok "BANG"!!!!! LOL, Im not hacking, Just the knowledge/experience of knowing you mess with the bull you will get the horns eventually.

 

[03_GMC]

I have the same rig and I have issues with it heating up. The radiator is brand new and once the temps get to 230 for coolant and trans the fans finally kick into high and it all quickly cools down. I will be adding a tru cool 40K but wanted to see pics of how guys put them in.

 

[Geotrash]

I’ve installed them in both 2012 and a 2007 Yukon XL Denali in the past few months. The difference between them is that the crossmember on the 2012 was welded to the A-frame, and it was bolted on the 2007. In both cases, I used a Dremel tool to cut away some of the crossmember flat surfaces to create clearance for the cooler pipes. I also had to cut away some of the plastic piece that holds the front bumper in place to create clearance for the relocated lines.

Some people say that you need to mount the cooler with the fittings facing up, but I didn’t do that and my coolers work fabulously anyway… Tested pulling a camper over a mountain pass my temps never got above 180°

I used the factory lines, and cut the passenger side line so I could swivel it 180° to connect to the longer cooler. I used a brass union to put the line back together. The driver’s side line has enough give to reach that side of the new cooler without any modifications.

One other thing, because the geometry on the 2007 was slightly different, I ended up having to cut 1 inch chunks of steel brake line to use as standoffs for the bottom crossmember. So the cooler on the 2007 sits about an inch further forward than it does on the 2012. I mentioning both so that you can adapt yours accordingly depending on what you find when you get in there.

Easy job, really. The pics are from the 2012.

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[Bill 1960]

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.

 

[Geotrash]

One more thing. These are the fittings you will need to snap the factory hard lines into the 40K cooler. Also, I used 3/4 inch long self-drilling screws designed for metal to attach the brackets to the crossmember and A-frame. I didn’t want to be drilling holes in steel with my air conditioning condenser sitting behind it. Easy peasy.

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[03_GMC]

Looks like I have a factory external trans cooler. Also just got my Denali tuned and GM sets these things up for failure. Your fans don’t go over a 60% duty cycle until after 222 degrees. Not I have 97% duty cycle by the time it hits 215.

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[Geotrash]

Looks like I have a factory external trans cooler. Also just got my Denali tuned and GM sets these things up for failure. Your fans don’t go over a 60% duty cycle until after 222 degrees. Not I have 97% duty cycle by the time it hits 215.

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Yup, that’s a factory cooler. Tear that thing out and throw it in the trash. Lol.

Didn’t know that about the fans. Thanks for that helpful tidbit - it explains why temps go up on these things sometimes, but only so far and they don’t seem to ever boil over.


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[Axm1096]

So what the average temp for the engine 220

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[03_GMC]

So what the average temp for the engine 220

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Well these gauges typically show 210 but the engine is really running about 192-195.


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[Geotrash]

Well these gauges typically show 210 but the engine is really running about 192-195.

Yup. Factory thermostat opens up as 195, so when I'm not towing, that's where she sits all day long. Towing is another story. And towing uphill in hot weather is yet another story that involves an extra transmission cooler and bigger radiator.

 

[03_GMC]

Yup. Factory thermostat opens up as 195, so when I'm not towing, that's where she sits all day long. Towing is another story. And towing uphill in hot weather is yet another story that involves an extra transmission cooler and bigger radiator.

Dude seriously get a tune! I know the bigger Ext trans cooler is a must but the new fan settings are amazing so far with the tune!!


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[Foggy]

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

 

[Geotrash]

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

Where did you mount your Derale?

 

[Foggy]

I have it mounted behind the bumper. I took out the oem aux cooler and
plumbed the derale in...
the oem cooler was right behind the intercooler, so I figured it was getting
a lot of heat from that
I still have the front apart due to installing my Snow Perf Meth Injection kit

I'll see if I can get some pics of it in the next day or two. I mounted the top of
it directly to the bumper bar itself. I'm going to run some small hardware
thru the license plate holes to support the lower part of it
And just putting the fan on toggle switch. It came with a thermostat, but
I want to have complete control... I'm ocd that way

 

[Geotrash]

Photos would be

I have it mounted behind the bumper. I took out the oem aux cooler and
plumbed the derale in...
the oem cooler was right behind the intercooler, so I figured it was getting
a lot of heat from that
I still have the front apart due to installing my Snow Perf Meth Injection kit

I'll see if I can get some pics of it in the next day or two. I mounted the top of
it directly to the bumper bar itself. I'm going to run some small hardware
thru the license plate holes to support the lower part of it
And just putting the fan on toggle switch. It came with a thermostat, but
I want to have complete control... I'm ocd that way

Photos would be amazing! And I'm OCD, too.

 

[03_GMC]

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

Changing the fan duty cycle settings in the ECM does help at highway speeds. It actually helps at all speeds. They aren’t dependent upon speed but actually on the temperature of the coolant. It sounds to me like you have a diesel swap in your truck which is a completely different ball game to what we are talking about. I agree that upgrading the tranny cooler is a must but it still shouldn’t be the only thing that is done. Like I stated earlier in this thread the factory programming for the fan duty cycles is crap and doesn’t move a lot of air until it starts getting harder to cool the engine and trans down. So again yes it will help at highway speeds. This isn’t a clutch fan setup, it is electric cooling fans.


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[Axm1096]

Im sorry i dont mean to steal the thread but i feel like theres a alot of support on this one can any one tell me why i have this leak and what gasket i need to repair it thank you in advance

 

[Foggy]

Changing the fan duty cycle settings in the ECM does help at highway speeds. It actually helps at all speeds. They aren’t dependent upon speed but actually on the temperature of the coolant. It sounds to me like you have a diesel swap in your truck which is a completely different ball game to what we are talking about. I agree that upgrading the tranny cooler is a must but it still shouldn’t be the only thing that is done. Like I stated earlier in this thread the factory programming for the fan duty cycles is crap and doesn’t move a lot of air until it starts getting harder to cool the engine and trans down. So again yes it will help at highway speeds. This isn’t a clutch fan setup, it is electric cooling fans.


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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

 

[Geotrash]

But keeping cool at a steady
60-70 mph while towing on grades in 90*+ weather presents a whole different set
of parameters

This is the part that concerns me and I want to be ready for *before* I run into trouble on a trip. Thanks for the input - very helpful.