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

[03_GMC]

That's a good idea and will likely do that, but I have a hunch that my engine cooling problem will be solved now that there isn't a massive transmission cooler in front of it. Time for an HP Tuners setup.

Oh I definitely agree that you helped it by relocating. Your factory settings on the tune will not allow a 97% duty cycle on the fans till your coolant is well into the upper 220 degree range. I need to do this upgrade to my Denali as well since we are doing a trip to Yellowstone this summer too.


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[Geotrash]

Oh I definitely agree that you helped it by relocating. Your factory settings on the tune will not allow a 97% duty cycle on the fans till your coolant is well into the upper 220 degree range. I need to do this upgrade to my Denali as well since we are doing a trip to Yellowstone this summer too.

Sweet! Hope y'all have a fabulous trip!

I've towed a lightly loaded, single-axle 5x10 cargo trailer across Kansas from Virginia to CO and back twice - once in May and once in July. The OAT driving westbound in July was 102ºF in a hot spell and the engine and transmission were both getting warm. For our trip to Yellowstone this August, I want my cooling system upgraded and fully sorted before we set out, so that's why I'm doing this work now while I still have time to experiment.

 

[03_GMC]

Sweet! Hope y'all have a fabulous trip!

I've towed a lightly loaded, single-axle 5x10 cargo trailer across Kansas from Virginia to CO and back twice - once in May and once in July. The OAT driving westbound in July was 102ºF in a hot spell and the engine and transmission were both getting warm. For our trip to Yellowstone this August, I want my cooling system upgraded and fully sorted before we set out, so that's why I'm doing this work now while I still have time to experiment.

Nice! When we moved to Texas from the Vail Valley in Colorado we pulled our Travel Trailer which was loaded to about 7500-8K#. I couldn’t keep the temps under control on the two mountain passes but once I got down on the plains it regulated great. Fast forward to last summer we borrowed our friends TT and went to Galveston. I had a hell of a time keeping the temps under 230 on both motor and Trans. That was even with a brand new radiator and cooling system flush. I am not risking it this time!!


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[Geotrash]

So tonight was a drive to soccer practice in 87° ambient temps. It took about 15 miles of driving to break 180° on the transmission temp, but then we sat in traffic for a while and the temperature crept up to 194°, before coming back down as the fan had turned on. Since the fan shut off temperature is 165° at the cooler inlet, it brought the transmission pan temperature down to about 178° before the fan shut off and the temperature started creeping back up again. Again, we will know more when we’re towing in the mountains this weekend, but I am very satisfied so far.

Also, when we parked at the game the fan was running, but shut off after maybe a minute, So having it wired into always on power doesn’t seem to be an issue so far.

 

[kbuskill]

So tonight was a drive to soccer practice in 87° ambient temps. It took about 15 miles of driving to break 180° on the transmission temp, but then we sat in traffic for a while and the temperature crept up to 194°, before coming back down as the fan had turned on. Since the fan shut off temperature is 165° at the cooler inlet, it brought the transmission pan temperature down to about 178° before the fan shut off and the temperature started creeping back up again. Again, we will know more when we’re towing in the mountains this weekend, but I am very satisfied so far.

Also, when we parked at the game the fan was running, but shut off after maybe a minute, So having it wired into always on power doesn’t seem to be an issue so far.

My main concern with it being hooked to constant power wouldn't be it running for too long after shutting the engine off.

My main concern would be a malfunction with the thermostatic switch getting stuck in the closed position allowing it to run continuously.

Odds are probably pretty slim but there is always that possibility. Having on a switched source would be a fail-safe just in case. It would suck to come out to a dead battery.

 

[Geotrash]

My main concern with it being hooked to constant power wouldn't be it running for too long after shutting the engine off.

My main concern would be a malfunction with the thermostatic switch getting stuck in the closed position allowing it to run continuously.

Odds are probably pretty slim but there is always that possibility. Having on a switched source would be a fail-safe just in case. It would suck to come out to a dead battery.

Yes, that’s my concern as well. That switch is not a real sturdy piece of kit either. I’ll definitely move it to a switched source.


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[03_GMC]

Anybody know the size of the factory fittings on the factory external trans cooler?


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[Geotrash]

This is the correct fitting for the factory cooler. It's a 9/16 threaded end with a 3/8" quick disconnect.

https://www.napaonline.com/en/p/NDP7305088?impressionRank=1&vehicleAddPDP=true

 

[Geotrash]

Some more data for those of you following along and for those considering this path. Picked up the camper this morning with an ambient temp of around 70ºF. It's about a 10 mile drive to the storage place each way - most of it on I-95. On the way out, the transmission temp hovered around 175ºF on the highway and was up to 180º once I slowed down and was maneuvering around the lot. The Derale's fan didn't need to come on. After picking up the trailer, on the highway, my transmission temp hung around 185-190ºF, also likely below the fan threshold. Once I got off the highway though, the temperature quickly rose to 199ºF and peaked at 205ºF as I maneuvered around the neighborhood and arrived at the house, but quickly settled back down to 198ºF once I stopped and was idling in park for a minute.

Engine coolant temp never broke 200ºF in either direction. So far, this seems to be a win for engine cooling, and I'm cautiously optimistic that it'll be able to keep the transmission cool enough (below 215ºF on the hills) when towing in warmer weather - especially on the highway. More data to come this weekend.

Does this jibe with what you guys who also have the Derale see when towing?

 

[Geotrash]

Pulled the camper out to Charlottesville this weekend and learned some more along the way, and thought I’d share for others who may be planning some towing this summer. I’ve also done a bunch of reading - some of it in GM manuals, and talked to a few people, including the guy who runs the local transmission shop who put my torque converter in. All of it makes me less concerned than I was with transmission temperature.

My coolant temps are under control now. It was 70°F ambient on the outbound trip and the highest coolant temp I saw was 199°F. On the way home it was 85°F ambient and I saw my coolant get to 212°F a couple of times, but no higher. The Cold Case radiator is a beast, and getting that Trucool 40k out from in front of it was the ticket. I'm also glad I bypassed the radiator's transmission fluid heat exchanger when I installed the Derale, or I'd likely still be seeing higher coolant temps, though likely still well within the safe zone. That said, if you live in a colder climate, the pre-heat function of that circuit is important, and I would recommend leaving it in the loop to get the trans temp to the minimum 150ºF in cold weather.

My trans temp seems to be under control as well, though about 15°F higher than I’d like. On the outbound trip, it settled in at 197°F with a rare rise to 205° when maneuvering through small towns, or parking the trailer and such. On the return, it settled in around 203°F with a few rare rises to 212°F when pulling out of a rest area or driving in traffic after getting off the highway. But I noticed that the Derale fan seemed to do a great job of capping the rise and the temp would start to fall again after being in traffic for a few minutes.

My next steps are to get as much ram air into the Derale as I can, and monitor on some longer trips we have coming up.

Also, one of the things I’ve learned is that Dexron VI is much more resistant to high temperature oxidation, and that transmission temps up to 235°F are considered normal by GM for the 6L80E. Above 270°F the fluid will degrade rapidly, and I’m a long ways from that. I have some trips planned over the blue ridge in the next couple of months, but I’m not sweating them right now. I'll likely just plan to make transmission fluid changes an annual event after towing season.