Keeping coolant and transmission temps under control when towing in the summer heat

[Sparksalot]

Also give us an idea which route you take from North Denver -- I-25 to Cheyenne, 287 to Laramie, or ?

287 is a pleasant drive.

 

[03_GMC]

Alright, well we made it to Rock Springs. It was a brutal trip. Roads were torn up in places and we had wind gusts up to 60MPH (gotta love WY) and a sustained wind of 25MPH. I can for sure say the Denali does not like thin non dense air, and hot air (it was 83-90 all day till dusk). Pulling the small trailer up to Genessee Park spiked temps like normal. It’s a gnarly little hill and give anything a workout. Driving up I25 North with the trailer wasn’t horrible. There was tons of construction and idiots to go around. We did take 287 because I hate the drive from Cheyenne to Laramie. There are a few good pulls going that way and I ended up with trans temps in the 220’s. Wasn’t there for long but also didn’t want to stay cool. Then came the shit show. West to East ish winds from before Laramie all the way to Rock springs. 3 gear was my best friend and we averaged 55-70MPH. Once the outside temp dropped below 70 the coolant temp didn’t budge and the trans stayed under 203. I kept the RPMs under 4K. This damn thing has 177K so it’s not enjoying it. I also believe I blew out my shock seal at some point because the fron left control arms and wheel and stuff had a oily fluid all over them when we got to Laramie. There was a few nasty bumps on 287 and one may have taken it out.

 

[Geotrash]

Alright, well we made it to Rock Springs. It was a brutal trip. Roads were torn up in places and we had wind gusts up to 60MPH (gotta love WY) and a sustained wind of 25MPH. I can for sure say the Denali does not like thin non dense air, and hot air (it was 83-90 all day till dusk). Pulling the small trailer up to Genessee Park spiked temps like normal. It’s a gnarly little hill and give anything a workout. Driving up I25 North with the trailer wasn’t horrible. There was tons of construction and idiots to go around. We did take 287 because I hate the drive from Cheyenne to Laramie. There are a few good pulls going that way and I ended up with trans temps in the 220’s. Wasn’t there for long but also didn’t want to stay cool. Then came the shit show. West to East ish winds from before Laramie all the way to Rock springs. 3 gear was my best friend and we averaged 55-70MPH. Once the outside temp dropped below 70 the coolant temp didn’t budge and the trans stayed under 203. I kept the RPMs under 4K. This damn thing has 177K so it’s not enjoying it. I also believe I blew out my shock seal at some point because the fron left control arms and wheel and stuff had a oily fluid all over them when we got to Laramie. There was a few nasty bumps on 287 and one may have taken it out.

Wow. Thanks for taking the time to post after such a long day. Sweet little camper you rented there, too, and it looks like the WDH is set up well for your truck.

I spent some years working on drilling rigs around Wamsutter and the Red Desert area along I-80 west of Rawlins, and I can confirm that the wind there is constant - even in the winter. I've seen some catastrophic mechanical failures in cars/trucks along that road, and helped a few stranded families get back on their way. The headwinds are enough to push any vehicles that are on the mechanical edge, right over it. The only mercy is that at nearly 8000' for most of the way, it's seldom very hot. 287 is always windy also - crosswinds. Today, I imagine you'll head up through Farson and Pinedale, along the wind River Range. Some beautiful country, for sure.

It's super helpful to me to know what you were getting for temps along the way, so thank you for taking the time to post. On the shock seal failure - did you get a chance to look under the hood and confirm the source? I only ask because those oil cooler lines run right past that area and are notorious leakers, as I'm sure you know.

 

[03_GMC]

Wow. Thanks for taking the time to post after such a long day. Sweet little camper you rented there, too, and it looks like the WDH is set up well for your truck.

I spent some years working on drilling rigs around Wamsutter and the Red Desert area along I-80 west of Rawlins, and I can confirm that the wind there is constant - even in the winter. I've seen some catastrophic mechanical failures in cars/trucks along that road, and helped a few stranded families get back on their way. The headwinds are enough to push any vehicles that are on the mechanical edge, right over it. The only mercy is that at nearly 8000' for most of the way, it's seldom very hot. 287 is always windy also - crosswinds. Today, I imagine you'll head up through Farson and Pinedale, along the wind River Range. Some beautiful country, for sure.

It's super helpful to me to know what you were getting for temps along the way, so thank you for taking the time to post. On the shock seal failure - did you get a chance to look under the hood and confirm the source? I only ask because those oil cooler lines run right past that area and are notorious leakers, as I'm sure you know.

Oh nice. Yeah I worked up here a lot when I was with UPRR. I checked the oil cooler lines and the fluid was not consistent with engine oil. It felt like power steering fluid or what I’d assume was shock fluid. I’m gunna take the rig through a do it yourself car wash and get it all cleaned off and maybe today I can pin point the issue. BTW after living closer to sea level and having 93 octane I can officially say I hate 91 and altitude…….

 

[Geotrash]

Oh nice. Yeah I worked up here a lot when I was with UPRR. I checked the oil cooler lines and the fluid was not consistent with engine oil. It felt like power steering fluid or what I’d assume was shock fluid. I’m gunna take the rig through a do it yourself car wash and get it all cleaned off and maybe today I can pin point the issue. BTW after living closer to sea level and having 93 octane I can officially say I hate 91 and altitude…….

Yeah, it's a double-edged sword for sure. A normally-aspirated engine loses about 3% of its horsepower for every 1,000' above sea level, and warmer air only makes it worse. So driving I-80 across southern WY, you were down on power somewhere around 21-25%. 91 Octane is all that engine can really use given the reduced air density in the cylinders. At the same time though, making less power means there's less work for the cooling system to do. The downside is having to hold 3rd gear just to keep going. I'd rather have the power and figure ways to keep it cool! Hmmmm... may be time for a supercharger. Lol.

 

[mikeyss]

I took my Tahoe up a long mountain road today, through Ward and up to Estes... Drove it hard and saw my trans hit 180 with my Tru cool. It was about 80 out, engine temps stayed normal.

 

[ddann19]

Hi All, the 2012 XL Denali is a towing beast, but after the cam upgrade, new HD torque converter, and adding the Tru-Cool 40K in front of the radiator, the engine itself is running warm now that we're getting into spring. Hauled our 6500 lb camper down to Virginia Beach this weekend in 83º ambient weather, and the engine coolant temps were running between 227º and 237ºF per the OBD2 stream most of the way, which translates to about 3/4 up the temp gauge on the dash. But that was only at speed... at idle in traffic it was running much cooler, around 205º. So that tells me that my fans are working fine (verified as well), but that the Tru-Cool cooler is likely robbing some of my radiator's capacity when the engine's working hard. Transmission stayed nice and cool the whole way, never getting above 180º.

After reading a bunch of posts from all of you, especially @kbuskill's experience with his Cold Case, I went with a GMT569A as I have oil coolers on both ends of my factory radiator. I like the fact that it's a 2-row with 1-1/4" wide tubes and is significantly deeper than the factory radiator. Hoping that this upgrade will finally make this truck what I want it to be for our summer camping season, including a 4000 mile trip west out to Yellowstone.

Anything else you guys can think of to shore this truck up for camper duty?

I’m leaving Illinois for Smith Mountain Lake on Sunday!

 

[03_GMC]

I took my Tahoe up a long mountain road today, through Ward and up to Estes... Drove it hard and saw my trans hit 180 with my Tru cool. It was about 80 out, engine temps stayed normal.

That’s great. So the biggest difference is we are all aluminum block and heads in the 6.2 whereas the Tahoe has the 5.3 which is an iron block. The iron block takes a long time to heat up compared to the all aluminum setup we have.

 

[03_GMC]

Alright so today went much better. 1st there was no wind!! Yay!!!!! Second the road was nice and gradual the whole way to Jackson. Trans temps never went above 200 and the coolant never saw over 215. I held 4 gear almost the whole way and sometimes ran in 5th. 3rd was necessary for a few long climbs but it wasn’t like the day before. So needless to say wind blows…….

I definitely recommend a aftermarket cooler. Also if you can find a good mounting spot for something bigger than the 30 row I purchased it wouldn’t hurt.

 

[Geotrash]

Alright so today went much better. 1st there was no wind!! Yay!!!!! Second the road was nice and gradual the whole way to Jackson. Trans temps never went above 200 and the coolant never saw over 215. I held 4 gear almost the whole way and sometimes ran in 5th. 3rd was necessary for a few long climbs but it wasn’t like the day before. So needless to say wind blows…….

I definitely recommend a aftermarket cooler. Also if you can find a good mounting spot for something bigger than the 30 row I purchased it wouldn’t hurt.

No wind on that drive? Better go get yourself a lottery ticket! Where will y'all be camping in that area? We reserved a spot for a few nights at Colter Bay and another few nights in West Yellowstone at a place called Yellowstone Holiday Resort. Glad your temps stayed under control for the trip. Maybe I should've investigated the American Volt coolers also. 30 row with a fan sounds just about perfect and I like that they offer thermostats with different ranges.

Side note: I think most of us on this thread running a Derale have the 13960, which is a 25-row cooler and is spec'd as having slightly more cooling capacity (46,000 BTUs with the fan running) than the Tru-cool 40K (45,000 BTUs). If anyone is interested, the next size up is the 40-row 13870. It still has the 6AN fittings but is another 3.5" taller and offers about 50% more cooling capacity. It would definitely hang down further than I would like, so I think with dropping the license plate down and opening up that lower grille fully, I'll finally have the cooling where I want it to be with the 25-row. The way mine was set up before hidden behind the license plate it was operating in a relative vacuum. Now I'll have the benefit of the ram air effect.

I prefer the Derale over the Tru-cool because instead of running at full cooling capacity all the time like the Tru-cool (passive), the Derale only runs at full capacity when the fan is running (active). That gives the transmission fluid the chance to get up to the minimum that GM specs for this transmission (150ºF) year-round.