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

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mikeyss

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Again, thank you. After studying all the part numbers for various model years and cooling system options, I landed on a 700 W motor designed for the enhanced cooling system spec (K5L) for the 2012 MY, along with an upgraded five bladed fan designed for the same enhanced system.


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Yes, for 2012 the fan design changed from a rimmed style blade, to just dual 5 blade with no rim around the blade. The non K5L in 2012 had dual 5 blade assembly with 500 W motors, and the K5L ones still had dual 5 blade but with 700 W motors, and I think the fans were a little larger. The older designs from 07-2010 had the 5/7 or 7/9 rimmed blade design, with 500 W or 700 W. It got confusing with all the different options for fans. Lol
 
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Dave
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Yes, for 2012 the fan design changed from a rimmed style blade, to just dual 5 blade with no rim around the blade. The non K5L in 2012 had dual 5 blade assembly with 500 W motors, and the K5L ones still had dual 5 blade but with 700 W motors, and I think the fans were a little larger. The older designs from 07-2010 had the 5/7 or 7/9 rimmed blade design, with 500 W or 700 W. It got confusing with all the different options for fans. Lol
Thanks for validating, Mike! Glad this info from all of us is here for future folks attempting the same job.
 
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Dave
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Just an update here. I towed our 6500 lb camper over the mountains of West Virginia twice this weekend, and made a few observations about the new setup. As a reminder, I now have the Tru-cool 40K transmission cooler sitting in front of the A/C condenser and a new Cold Case double-row radiator. All of this is cooling a drivetrain that makes an extra 50-60 HP & TQ over the stock 6.2L, thanks to a stage 2 truck cam upgrade.

Before any of those cooling system mods, my engine would run 200º-230º and my transmission would run 180º-235º when towing in 80º weather, depending on terrain.

After adding just the Tru-cool, my transmission ran much cooler, as expected, between 150º-180º when towing over the hills, which was a huge improvement, but my engine would run much warmer than before, between 220º-230º when towing on relatively flat ground in 80º weather, and I stayed out of the mountains as a result until I could sort it out.

Then, after adding the Cold Case radiator, my transmission temps are still nice and cool, and my engine temps now run 200º-210º when towing on flat ground, and it only gets above 220º when pulling up longer, steeper grades. In general, that's a significant improvement but still may not be enough.

On the way home yesterday, we climbed some long hills and because of traffic on I-81 had to keep our speed at 70 mph or above. It was about 78º outside and I noticed a couple of times my engine temp crept up to 240º but only for brief moments before cooling back down to 230º while still climbing the same grade. My guess is that's when the fans would kick into high gear and wrangle the temp back down. Also, the transmission never got above 180º.

Long story short, my conclusion is that while the Tru-cool is fabulous, its exceptional performance comes at the expense of radiator and engine cooling performance because of its positioning. I'll know more as the summer heat ramps up and we take some more trips, but my guess is that I'll have to take some additional steps to restore the balance of cooling system performance between the engine and transmission. I may experiment with a remote-mounted Derale fan-assisted transmission cooler in order to unblock the radiator. I'll update this thread as I experiment.

If any of you have any other ideas or things I should consider, I would welcome them - especially ideas for how/where to mount a Derale cooler, or even to re-position the Tru-Cool.
 

kbuskill

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Just an update here. I towed our 6500 lb camper over the mountains of West Virginia twice this weekend, and made a few observations about the new setup. As a reminder, I now have the Tru-cool 40K transmission cooler sitting in front of the A/C condenser and a new Cold Case double-row radiator. All of this is cooling a drivetrain that makes an extra 50-60 HP & TQ over the stock 6.2L, thanks to a stage 2 truck cam upgrade.

Before any of those cooling system mods, my engine would run 200º-230º and my transmission would run 180º-235º when towing in 80º weather, depending on terrain.

After adding just the Tru-cool, my transmission ran much cooler, as expected, between 150º-180º when towing over the hills, which was a huge improvement, but my engine would run much warmer than before, between 220º-230º when towing on relatively flat ground in 80º weather, and I stayed out of the mountains as a result until I could sort it out.

Then, after adding the Cold Case radiator, my transmission temps are still nice and cool, and my engine temps now run 200º-210º when towing on flat ground, and it only gets above 220º when pulling up longer, steeper grades. In general, that's a significant improvement but still may not be enough.

On the way home yesterday, we climbed some long hills and because of traffic on I-81 had to keep our speed at 70 mph or above. It was about 78º outside and I noticed a couple of times my engine temp crept up to 240º but only for brief moments before cooling back down to 230º while still climbing the same grade. My guess is that's when the fans would kick into high gear and wrangle the temp back down. Also, the transmission never got above 180º.

Long story short, my conclusion is that while the Tru-cool is fabulous, its exceptional performance comes at the expense of radiator and engine cooling performance because of its positioning. I'll know more as the summer heat ramps up and we take some more trips, but my guess is that I'll have to take some additional steps to restore the balance of cooling system performance between the engine and transmission. I may experiment with a remote-mounted Derale fan-assisted transmission cooler in order to unblock the radiator. I'll update this thread as I experiment.

If any of you have any other ideas or things I should consider, I would welcome them - especially ideas for how/where to mount a Derale cooler, or even to re-position the Tru-Cool.

Since you have a GMC, maybe stick the trucool down behind the "lower grille" in your bumper.:shrug:
 

HD_LS

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Are you still running the transmission fluid through the radiator tank cooler, before sending it to the Tru-Cool 40K? I second the previous recommendation to route the transmission fluid to the Tru-Cool only, and keep it out of the radiator tank. This will restore some balance by not having your engine coolant directly heated by the transmission fluid. This will help whether you move the transmission cooler or not.

Are your fans programmed to come on at cooler than factory temperatures? I also like the idea of using the more powerful fan motors.


In case the thermostat max opening area is a coolant flow restriction: Remember that flow restrictor you put in the hose between the upper rad tank fitting and the coolant tank? You could put a valve in to bypass that restricion when you are towing. (since that flow bypasses the thermostat)
 
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Dave
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Since you have a GMC, maybe stick the trucool down behind the "lower grille" in your bumper.:shrug:
That's a good idea. I will investigate that. It's backed by a solid plastic piece right now, but that could be drilled out.
 
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Dave
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Are you still running the transmission fluid through the radiator tank cooler, before sending it to the Tru-Cool 40K? I second the previous recommendation to route the transmission fluid to the Tru-Cool only, and keep it out of the radiator tank. This will restore some balance by not having your engine coolant directly heated by the transmission fluid. This will help whether you move the transmission cooler or not.

Are your fans programmed to come on at cooler than factory temperatures? I also like the idea of using the more powerful fan motors.


In case the thermostat max opening area is a coolant flow restriction: Remember that flow restrictor you put in the hose between the upper rad tank fitting and the coolant tank? You could put a valve in to bypass that restricion when you are towing. (since that flow bypasses the thermostat)
Routing the transmission cooler direct is a good idea, but my worry with that is for the winter when there is benefit to warming the fluid a bit from cold. But, I could also add a thermostatic control valve in the circuit, I suppose.

Fans are still programmed to come on at the factory temps. I bought the 700w fan motor for the drivers side, along with the correct fan blade, and will install both this weekend.

Thanks for offering some good ideas.
 

HD_LS

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What motor and fan blade part numbers did you settle on? Where did you buy them from?
 

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