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

[Foggy]

Hot trans fluid OUT to radiator
Then IN to aux cooler
then from aux cooler back to radiator...

I don't remember which line is which on the transmission itself... but if you have
the stock aux cooler, you could follow the line from it to the trans and you'd know.
I believe i just search engined it at the trans itself.. Then I knew for sure

 

[Geotrash]

Sorry, I was not being clear enough in my other post...

What I wanted to know is. What is best plumbing wise oil going through stock radiator cooler then to aux cooler or the other way around?

Also what are the inlet and outlet lines on the radiator trans cooler?

What Foggy said is correct. Also, the fluid flows from the bottom of the radiator’s cooler to the top in the factory setup, so the line coming into the bottom of the radiator is the hot line from the transmission. Then plum from the top of the radiator to the cooler, and then from the cooler to the other line back to the transmission, which is the cool line.

 

[Geotrash]

Update from the road. Made it to Cheyenne, WY yesterday. Pulling across Nebraska we gained 5000’ in elevation and the outside air temp was 94°F with a 20mph crosswind from the south. I didn’t push the truck and let it hold 65 mph the whole way. Prior to that leg of the trip, the transmission spent most of its time in 5th at around 2k rpms, but yesterday it spent most of its time in 4th at 2750 rpms. Not bad. Transmission stayed steady around 200°F with one spike to 210° on a long climb. The coolant temp held steady at 210°F on the gauge most of the way, but crept up to 3/4 (235°F) on a few of the long climbs, but as before the fans seemed to have kicked on and it came right back down. So far, I’m very happy with this setup.

 

[Tozan]

Thanks guys.

 

[Cincikid]

Update from the road. Made it to Cheyenne, WY yesterday. Pulling across Nebraska we gained 5000’ in elevation and the outside air temp was 94°F with a 20mph crosswind from the south. I didn’t push the truck and let it hold 65 mph the whole way. Prior to that leg of the trip, the transmission spent most of its time in 5th at around 2k rpms, but yesterday it spent most of its time in 4th at 2750 rpms. Not bad. Transmission stayed steady around 200°F with one spike to 210° on a long climb. The coolant temp held steady at 210°F on the gauge most of the way, but crept up to 3/4 (235°F) on a few of the long climbs, but as before the fans seemed to have kicked on and it came right back down. So far, I’m very happy with this setup.

Are you running the A/C as well with those numbers?

 

[Geotrash]

Are you running the A/C as well with those numbers?

Yes. Both front and rear A/C set to 71°F.

 

[Geotrash]

Update: After 2 more relatively short driving days, we made it to Colter Bay in Grand Teton NP, early this afternoon after a stopover in Lander. We had much cooler weather both days (65°F yesterday and upper 50s today), but with 25 mph headwinds, yet the transmission stayed around 196°F and topped out at 205° after a long climb into the wind yesterday in 3rd gear. Held between 60-65 mph on the 2-lanes, but had to spend a lot of time in 3rd gear climbing Togwatee pass today in the rain, yet the coolant temp never moved off the 210° peg and the transmission stayed below 200° for the entire climb. Held 50-55 mph, no problem. Outside temp at the top of the pass was 37°F and there was fresh snow in the tundra. Winter is coming.

Really happy with the way this engine and cooling setup is performing now. I think I finally have everything dialed in (cam, radiator, trans cooler, torque converter) to the point that I’d take it anywhere in the country in the summer, with our 7000 lb camper in tow. The 6.2 is a superb engine for this duty, and the XL Denali is the best, most comfortable vehicle for long family road trips I’ve ever owned.

 

[Doubeleive]

ambient temperatures here have been under 100 (mostly) a few 80'ish days, trans temps have been approx double the ambient with the tru-cool located in the lower grill, I'm thinking I still want to run the fan kit with it just haven't pulled the trigger yet, been doing some early xmas shopping

 

[Geotrash]

ambient temperatures here have been under 100 (mostly) a few 80'ish days, trans temps have been approx double the ambient with the tru-cool located in the lower grill, I'm thinking I still want to run the fan kit with it just haven't pulled the trigger yet, been doing some early xmas shopping

That’s helpful data, Wes. I still have the 40k in front of the radiator on my ‘07 back home. I’ll either drop it below the bumper this fall or put a Derale with integrated fan in below like I have in the ‘12.

 

[Cincikid]

I did some moderate hills yesterday pulling my 5000lb camper and my engine temp reached 237 and it was about 100 outside. My trans temp reached a max of 208 so I'm not worried about that, just my engine temp. The rest of the trip I ran with no AC and it peaked around 220. I have a Derale transmission cooler and my next mod might be to relocate it to the lower intake. But what I don't understand is that pulling the camper in traffic or around town in stop and go is fine and the temps stay normal, but on the highway when it should be getting tons of airflow is when I seem to have issues? Here's a screenshot of my numbers.