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Discussion Starter #21
I can't imagine what the temps would be if towing our camper in Joshua Tree area when it is 114*F, which is what it was when we were there with our truck, not towing.
I suppose that's a concern too. Probably a clear time you should remove those vent blocks. Also maybe cut 10 mph off the speed you would normally pull going up hill.

Has anyone reported towing in conditions like that?
 

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The short answer is no, they don't drive each other. This is abundantly clear based on empty fluid temps. If fluid temps were driven by other fluid temps then they would always follow each other.

Not only that, the coolant temp sensor isn't reading radiator temps. It's reading the temp as it leaves the engine. By the time the coolant flows to the bottom of the radiator it is much cooler.

Oil temps increase as the oil is worked harder (higher RPMs). Coolant temps increase due to higher consistent power (heat) output from the engine, and so on.

There is no need for a larger radiator.

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Discussion Starter #23
Not only that, the coolant temp sensor isn't reading radiator temps. It's reading the temp as it leaves the engine. By the time the coolant flows to the bottom of the radiator it is much cooler.
I realize that, but the fact that the engine coolant rises significantly means that either that the water coming in is warmer or that there isn't enough water flowing through to maintain the same temperature (but maybe they purposefully want to limit flow). It's one or the other (or possibly the third factor I already mentioned that the reading could be after the oil heat exchanger and reflecting the heat released from the oil).

This may be an area where less information is better than more, sort of like regen information. If all I had was the dummy dash temperature gauge I wouldn't be thinking of any of these things because none of there values are serious.
 

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I realize that, but the fact that the engine coolant rises significantly means that either that the water coming in is warmer or that there isn't enough water flowing through to maintain the same temperature (but maybe they purposefully want to limit flow). It's one or the other (or possibly the third factor I already mentioned that the reading could be after the oil heat exchanger and reflecting the heat released from the oil).

This may be an area where less information is better than more, sort of like regen information. If all I had was the dummy dash temperature gauge I wouldn't be thinking of any of these things because none of there values are serious.
This is a case where more information is hurting you. Literally every vehicle will have increased coolant temps under load, that's just how thermodynamics and the cooling systems work. If you had a radiator that maintained 172-174F at 100% engine load in the desert then the cooling system would be overcooled under all other conditions and the thermostat would be unable to maintain equilibrium, the coolant in the engine would warm up, the t-stat would open, there would be an inrush of cold coolant, the t-stat would close. Rinse and repeat. The reading from the temp sensor would constantly be changing.

Expecting the coolant temp to maintain the minimum allowed operating temperature under all conditions is where you're going wrong. The normal coolant temperature is a range, not a specific temperature. Even with the big class 8 trucks. For example, a Cummins ISX15 has a normal coolant temp range of 180F-220F. Similarly, the normal oil temp range is 200-245F.

You're looking for problems where there are none. A misunderstanding of how the systems function leads to false assumptions and thinking there are problems when everything is fine.
 

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Discussion Starter #25
This is a case where more information is hurting you.
I think that's what I said. ;)

But at the same time I have this desire to understand how things work and interact. And to some extent you do too, otherwise you would have never removed your vent covers.

I can't say I've ever monitored transmission temps on any other vehicle, but I have monitored oil temps and I don't remember them tagging along so closely. But then I don't know how those engines were set up either. Also both the coolant and oil on this engine runs cooler under normal driving than most the other engines I've had. That's why I'm not terribly concerned about it, but I do still want to know how things interact.
 

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I think that's what I said. ;)

But at the same time I have this desire to understand how things work and interact. And to some extent you do too, otherwise you would have never removed your vent covers.

I can't say I've ever monitored transmission temps on any other vehicle, but I have monitored oil temps and I don't remember them tagging along so closely. But then I don't know how those engines were set up either. Also both the coolant and oil on this engine runs cooler under normal driving than most the other engines I've had. That's why I'm not terribly concerned about it, but I do still want to know how things interact.
Well, as I said in my earlier post the oil temp is changing more based on the oil itself being worked and not a change in coolant temp. If you want to test this yourself, take your unloaded truck out on the freeway and run the trans in 5th gear instead of 6th. When you're towing have you noticed the truck spends most of its time in 5th gear with downshifts to 4th depending on headwinds or hills? Rarely, if ever, runs in 6th? That is the primary cause of the oil temps increasing, the increase in engine RPMs, the higher oil pressure, and the additional load on the bearings.

Coolant temp rises because the engine is generating more heat due to higher engine load.
Oil temp rises because the oil is being worked harder due to higher RPMs. Some additional heat is generated due to the oil jets under the pistons which are used to help cool the pistons.
Trans temp rises because the fluid is being worked harder under load and any added friction or slippage while under load contributes to trans fluid temp increases. It is also affected by ambient temps.

The main reason you see temps trending together when towing or under load is because all of those systems are under higher load. As such, temps for all of them are going to increase. That's the correlation. The higher temps from one system are not the cause of increases in the other systems.

If you do what I mentioned above and run on the freeway in a lower gear you can see the affect it has on various temps. They key point to remember is that as long as none of the temperatures leave the normal range when under load then everything is working as designed. I did remove the panels on my truck, not because I was worried the trans was running too hot but because the lower temps will help with fluid life by reducing oxidation and the intervals at which I need to change the fluid.

I wish I would've taken a pic of my temps after driving home in the wind last night. I still have my RTT on and when I run 74-75 on the freeway against the wind often times it'll just sit in 5th since it's right on the edge of upshifting. This was the case for about 20 minutes on the freeway, it was running in 5th while doing 74-75mph. Trans temps ran around 140-150F, coolant temp below 180F, and the oil temps were around 205F, IIRC. All very different temps from each other, which I why I said the unloaded temps clearly show the temps of the systems really aren't tied together. If they were then they would be much closer under all conditions. The increase under load is due to the load, not due to proximity to each other and their fluids. Oil temp is the easiest to manipulate because it can be done under load and with an empty truck just by changing RPM because working the oil generates heat.
 

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Discussion Starter #27
Well, as I said in my earlier post the oil temp is changing more based on the oil itself being worked and not a change in coolant temp. If you want to test this yourself, take your unloaded truck out on the freeway and run the trans in 5th gear instead of 6th. When you're towing have you noticed the truck spends most of its time in 5th gear with downshifts to 4th depending on headwinds or hills? Rarely, if ever, runs in 6th? That is the primary cause of the oil temps increasing, the increase in engine RPMs, the higher oil pressure, and the additional load on the bearings.
Thanks, I'll give that a try, but I also think another factor is burning a lot more fuel. Almost twice as much. But doing it empty will focus on your factors.

Trans temp rises because the fluid is being worked harder under load and any added friction or slippage while under load contributes to trans fluid temp increases. It is also affected by ambient temps.
I really don't understand automatic transmissions that well. My first car with an automatic (as opposed to my wife's) was a 2013. I haven't tended to think a lot about them other than when I read about a locking torque converter or a dual clutch model.

But I do recall being a teenager with my dad when he was driving a motorhome with a manual transmission (A Cortez if I recall correctly) and he commented that the grade must not be too bad because the RPMs weren't rising. I had to point out it was a manual transmission and RPMs to speed were pretty well set in stone for any given gear.
 

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I have tranny cooler with fan after tranny cooler in radiator and I tow everyday in AZ 3500-5000 I can maintain always less than 190. If going up hills 205 is max I’ve seen. But normal towing with cooler 185-192
 
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