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Discussion Starter #21
The thing that weirds me out about the trans cooler is that its AFTER the radiator end tank in the flow path. I suppose having the larger cooler means they just are flowing less Trans fluid through the cooling loop since its coming out colder on the backside. less fluid means its offloading less heat to the coolant.

I still cant figure out why my truck never exceeds 208 without the radiator end tank in the loop. Its 100% fine so far. I am guessing it is because of my tunes that keep the torque converter locked all the time.
 

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The thing that weirds me out about the trans cooler is that its AFTER the radiator end tank in the flow path. I suppose having the larger cooler means they just are flowing less Trans fluid through the cooling loop since its coming out colder on the backside. less fluid means its offloading less heat to the coolant.

I still cant figure out why my truck never exceeds 208 without the radiator end tank in the loop. Its 100% fine so far. I am guessing it is because of my tunes that keep the torque converter locked all the time.
Don't you also have an adjusted fan strategy?

I still think the larger trans cooler provides two benefits. 1) It doesn't dump extra heat into the coolant and 2) When it's open at 195 it's actually pulling some heat from the coolant when temps are high.

The reason I suspect #2 is also going on, is because in the stock configuration under extreme heat load conditions, my ECT would get hot, THEN the trans would start to get hot. This seemed to be a caused by high ECTs and the stock trans cooler not able to do anything for the fluid.
 

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Mass,

The reason for the coolant->trans HX first is the cold side of the radiator is always hotter than ambient (on a warmed up engine). If you had the air-cooled HX first you could potentially cool the tranny fluid cooler than the cold side of the radiator, meaning the tranny fluid would be putting heat back into the engine. All 3 of the trucks I've towed with were set up this way.

I'm a fan of having a coolant heat exchanger on the tranny fluid. When I'm crawling in stop/go traffic or going up a dirt road the radiator fans aren't going to pull anything across the air-cooled HX as it's in front of the AC condenser with no ducting. That's where the coolant HX really comes into play as it's still able to reject heat. I'll be testing this theory this afternoon. Our trip this weekend will require about 8-miles up a steep dirt fire road. I'll be running maybe 10mph max as it's super bumpy and I don't want to destroy my trailer.
 

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Discussion Starter #24
Don't you also have an adjusted fan strategy?

I still think the larger trans cooler provides two benefits. 1) It doesn't dump extra heat into the coolant and 2) When it's open at 195 it's actually pulling some heat from the coolant when temps are high.

The reason I suspect #2 is also going on, is because in the stock configuration under extreme heat load conditions, my ECT would get hot, THEN the trans would start to get hot. This seemed to be a caused by high ECTs and the stock trans cooler not able to do anything for the fluid.
I dont know how much different the fan strategy is on my tunes. With the gearhead tow tune on my last trip it seems to be turning on high around 105C which I believe is only a little cooler than stock.

Mass,

The reason for the coolant->trans HX first is the cold side of the radiator is always hotter than ambient (on a warmed up engine). If you had the air-cooled HX first you could potentially cool the tranny fluid cooler than the cold side of the radiator, meaning the tranny fluid would be putting heat back into the engine. All 3 of the trucks I've towed with were set up this way.

I'm a fan of having a coolant heat exchanger on the tranny fluid. When I'm crawling in stop/go traffic or going up a dirt road the radiator fans aren't going to pull anything across the air-cooled HX as it's in front of the AC condenser with no ducting. That's where the coolant HX really comes into play as it's still able to reject heat. I'll be testing this theory this afternoon. Our trip this weekend will require about 8-miles up a steep dirt fire road. I'll be running maybe 10mph max as it's super bumpy and I don't want to destroy my trailer.
I guess I meant more like why would a bigger exchanger AFTER the end tank make a difference in the ECT's. It is going through the end tank heat exchanger before the bigger air cooler anyways so its still hitting the coolant hot.

I havent done a lot of low speed driving with the trailer but still i havent seen over 208 yet.
 

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I guess I meant more like why would a bigger exchanger AFTER the end tank make a difference in the ECT's. It is going through the end tank heat exchanger before the bigger air cooler anyways so its still hitting the coolant hot.

I havent done a lot of low speed driving with the trailer but still i havent seen over 208 yet.
I see your point. I think it has to do with the tranny being a loop. We don't necessarily care about the instantaneous heat transfer, just that it keeps the whole tranny loop cooler. I think with the bigger air HX you are sending cooler fluid back to the tranny which in turn lowers the temp of the fluid being sent to the radiator. At a lower tranny temp you'll actually transfer less heat to the coolant as heat transfer is governed by the temperature difference between the two fluids. The closer they are to each other the less heat you will transfer.
 

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Mass,

The reason for the coolant->trans HX first is the cold side of the radiator is always hotter than ambient (on a warmed up engine). If you had the air-cooled HX first you could potentially cool the tranny fluid cooler than the cold side of the radiator, meaning the tranny fluid would be putting heat back into the engine. All 3 of the trucks I've towed with were set up this way.

I'm a fan of having a coolant heat exchanger on the tranny fluid. When I'm crawling in stop/go traffic or going up a dirt road the radiator fans aren't going to pull anything across the air-cooled HX as it's in front of the AC condenser with no ducting. That's where the coolant HX really comes into play as it's still able to reject heat. I'll be testing this theory this afternoon. Our trip this weekend will require about 8-miles up a steep dirt fire road. I'll be running maybe 10mph max as it's super bumpy and I don't want to destroy my trailer.
No issues with the truck this weekend pulling the trailer. I was crawling for 1.5-hours to go about 10-miles up a rough dirt road. Average grade was about 7%. It was 90-95 until I got to the upper elevations. With the AC going the radiator fan was on high most of the time. ECT stayed right around 190 and TFT stayed right around 195 the whole way.

Also before the dirt I had to climb a 3-mile grade that averaged 8% with a peak of 9%. 100F ambient. Truck did great. ECT didn't hit 240F until the very top where the grade increased to 9%. TFT never got over 205F. AC was blasting the whole way up. Truck held 45mph in 3rd no problem until the very end at the 9% part it had to downshift to 2nd. I think this Saudi cooler is my golden ticket! (kids were watching the old Willy Wonka while I was towing, LOL)
 

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Dave I think that's pretty conclusive, because you have the same Saudi cooler I do, but without the other upgrades (Superstant, CRP manifolds, etc. ) Thanks for updating. You have to rename your "Nemesis" hill now. lol.
 

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Discussion Starter #28
Towed up to Teton NP and there is really only one big climb just before getting to Star Valley, WY. I tried to use the “downshift and use the rpms to do the work” technique unsuccessfully. It was probably 80F at the bottom of the climb(didn’t actually look) and 76 when i summited.

It got nice and hot. Was in 3rd gear at just over 4k rpm but was going too fast to hit 2nd. Right at the top my Forscan app said i clipped 244F. IAT was pushing 150. Trans hit 211.

After cresting the hill the needle dropped back to center in probably 15 seconds.
 

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Discussion Starter #29
Well, its about that time of year to start revisiting this nonsense again. Still kinda of want to see what happens if I remove half of the shroud to let the radiator breath.
 
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You'd probably be better off with an intercooler upgrade. Hot air is still hot air when moved in larger volume.
 

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Discussion Starter #31
You'd probably be better off with an intercooler upgrade. Hot air is still hot air when moved in larger volume.
I have an AFE Intercooler. Its not perfect but still much better than stock.
 

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I know what you have, just taking a dig at the lack of performance you reported from it.:p
 

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Discussion Starter #33
Don't you also have an adjusted fan strategy?

I still think the larger trans cooler provides two benefits. 1) It doesn't dump extra heat into the coolant and 2) When it's open at 195 it's actually pulling some heat from the coolant when temps are high.

The reason I suspect #2 is also going on, is because in the stock configuration under extreme heat load conditions, my ECT would get hot, THEN the trans would start to get hot. This seemed to be a caused by high ECTs and the stock trans cooler not able to do anything for the fluid.
I was thinking about this sporadically the last few days and it would be interesting to know how hot the coolant is leaving the radiator at any given time. If the coolant was >200F at the outlet then it could help but that seems really high if the coolant is only leaving the engine at 245 before limp mode strikes.
 

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Discussion Starter #34
I was thinking about this sporadically the last few days and it would be interesting to know how hot the coolant is leaving the radiator at any given time. If the coolant was >200F at the outlet then it could help but that seems really high if the coolant is only leaving the engine at 245 before limp mode strikes.
So this may be a legit thing, using the Transmission as a heat sink for the engine coolant under high loads. I stumbled across this the other day on the Mishimoto radiator report:

167200


So the outlet temp on the radiator was approaching 190°F on 15 second pulls and certainly didn't look like it was close to stopping. Now make your pull a few minutes long and I wonder where you end up?
 

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It does precisely that because the trans fluid goes through the end tank of the radiator. If it's cooler than what the coolant is, it's going to scavenge heat. I have the Full Race radiator and while it does help by providing a bit more overhead before heat soak, the fail mode is the same. The chart clearly shows this with the Mishimoto as well. You might get down the road a few more miles before having to take your foot out of it, but add in the larger trans cooler on top of it, and now you flatten that bump even more. FLATTEN THE CURVE!
 

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Discussion Starter #36 (Edited)
It does precisely that because the trans fluid goes through the end tank of the radiator. If it's cooler than what the coolant is, it's going to scavenge heat. I have the Full Race radiator and while it does help by providing a bit more overhead before heat soak, the fail mode is the same. The chart clearly shows this with the Mishimoto as well. You might get down the road a few more miles before having to take your foot out of it, but add in the larger trans cooler on top of it, and now you flatten that bump even more. FLATTEN THE CURVE!
I understand the heat will transfer, My hang up was on whether the coolant actually gets hot enough leaving the radiator to offload heat. If my engine coolant outlet is at 245 and my trans fluid is at 210, that means my radiators temperature drop has to be something less than 35 degrees for heat transfer to even start to happen. In other words, it wont transfer heat to the trans if the radiator outlet is cooler than 210.

That seem like much like an extremely small temperature drop through the radiator, but i guess it’s realistic.
 

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I think it just increases the size of the sink on the ECT. So in order to push it 1 degree past 195, it takes more energy because you have the trans soaking up the heat. I thought the trans opened up at 195? In my mind I see it as broadening that curve. It will still get hot to overheat, but the rate isn't as quick, so you have more time to react for a downshift or pullover.

I'd love to have a in/out coolant temp setup on the truck on a small gauge. It would greatly aid when you need to take your foot out of it when towing grades.
 

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Discussion Starter #38
I think it just increases the size of the sink on the ECT. So in order to push it 1 degree past 195, it takes more energy because you have the trans soaking up the heat. I thought the trans opened up at 195? In my mind I see it as broadening that curve. It will still get hot to overheat, but the rate isn't as quick, so you have more time to react for a downshift or pullover.

I'd love to have a in/out coolant temp setup on the truck on a small gauge. It would greatly aid when you need to take your foot out of it when towing grades.
It does open at 195 but when I've towed I have never seen it really sit much below 205, even now with my AFE Trans pan and like 12 extra QTS of trans fluid.
 

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It does open at 195 but when I've towed I have never seen it really sit much below 205, even now with my AFE Trans pan and like 12 extra QTS of trans fluid.
Do you have the fat trans cooler?
 

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Discussion Starter #40
Do you have the fat trans cooler?
I have the expedition cooler. It never goes over 208, but also doesnt go much below 205.
 
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