Hey All,
I am new to this forum after buying a 2012 F-350 King Ranch Diesel. I am eventually going to purchase a camping trailer to pull with this rig. I am thinking of bypassing the radiator with my transmission coolant lines. I did this on another vehicle and it worked GREAT! That vehicle was a 2001 Isuzu Trooper with that crummy 4L30-E transmission. My trans temps stay round 170 to 175 on the freeway which is far better than the 190 to 200 range that GM says they will run. At any rate, has anyone done this on the 2011-2017 F-250 to F-350 applications? I was thinking of adding a filter or two with a fan-cooler from B & M Racing Equipment. Thanks

 

No need to do that, you'll gain nothing. The 6.7 has a robust cooling system that's very capable. The torque shift tranny has an internal t-stat and will run at that temp. no matter what you do to it.

 

Thanks 69cj for that! That's good to know! What if I am pulling that trailer that I was talking about? Will the trani temps stay the same?

I absolutely love that truck! It is loaded like yours is and on our present trip to Florida it was so pleasant and very comfortable. There are only 3 of us so there was plenty of room. We just have to work out a plan for more storage room back in the truck bed as that tool box is too small. Thanks

 

Temps rise a little when in the mountains and such but nothing to worry about.

 

Chuck, your truck can pull anything you would ever buy and all you need to do is feed it diesel, tires, and brakes.

 

And DEF, lol.

 

A good rule of thumb on acceptable transmission temps is 100 degrees above ambient. I sure wouldn't mess with Ford's factory setup.

 

I tow heavy and the tranny temps stay around 200-210 most of the time. Well within the spec's.

 

At 10k to 11k I'm probably not in the "heavy" trailer category. But I tow over Colorado mountain passes where 11,000' elevation is not unusual. My last trip over an 11,000' pass had my engine oil at 243° F and transmission at 232° F. That seems hot to me but that only lasts for about 20 minutes on the way up.

 

Why would you want to do this? It doesn't make any sense to bypass the radiator. It will just reduce the amount of transmission cooling, and that's not a good thing.

 

All I can figure is that it keeps the 200°+ coolant from heating the transmission, where if the transmission settles on a 200° operating temp and the coolant is running at 219°, the transmission won't be collecting more heat than it makes.

Of course, I defer to you professionals, but I'd have to think that slight heat exchange in both directions is factored into the engineering of the entire cooling system, so there could be unintended consequences.

 

The radiator NEVER heats the transmission. If the coolant is at 219°F leaving the engine it will be considerably cooler after it runs through the radiator to the cool side, and that's where the transmission cooler is located.

There is no heat exchanged into the transmission. We did investigate this, and the only way to heat the trans was to use coolant just leaving the engine. you need either the upper radiator hose or the heater hose to the heater.

 

I haven't had my F-350 long enough to start looking at the plumbing. The transmission line go into the radiator on the side, correct? I would assume that this is the bottom of the radiator and it exits out the bottom of the radiator also?

I replumbed the transmission cooler lines on my 1/2 ton truck when I added an aftermarket cooler. This was in addition to the existing OEM cooler. There was an ongoing debate over if the engine coolant in the radiator would heat up the transmission fluid. In that truck it was almost a certainty that it would, but only to an extent. There was no thermostat on the transmission, so as soon as the transmission started working it was pumping fluid through the coolers and radiator. In the winter this meant that the coolant going through the radiator got warmed up before returning to the transmission (this is a good thing). Based on what Mark said, in the summer it would be a wash as the engine coolant at the bottom of the radiator would be cool enough to probably provide additional cooling of the transmission fluid.

Thank you for your post Mark. This is good info.

 

That's correct Ruschejj, bypassing the radiator allows for a slower rise and faster cooling of ATF temps below the engine coolant temps utilizing both a passive and an active fan cooler(Ie. my 2001 Trooper). An example would be after climbing a hill when ATF temps climb up, the ATF would cool faster and eventually return to temps well below the engine coolant temps by not passing through the radiator again. Those temps run anywhere from 165 to 175 on a flat freeway.

I used my 2001 Isuzu Trooper as an example of bypassing the radiator. I watch my Scan-Gauge to monitor the ATF temps and that's exactly what it does. Its 4L30-E tranny runs hotter than most staying in the range of 215 to 235 without being bypassed. As a result when it gets to the 125,000 to 150,000 mile range it needs a rebuild.

Since driving my 2012 F350 and watching the gauge temps I noticed that the tranny stays mostly in the 190's range. This is well within specs range I'm sure to not cause degradation of tranny components. I had asked earlier about pulling a camping trailer and one of you kindly advised me that ATF temps do go up some but nothing to be alarmed about. Thanks for your input!

 

That's wishful thinking, but it is NOT true! Read what I wrote, above.

THE RADIATOR NEVER HEATS THE TRANSMISSION FLUID.

I don't think it can be made any clearer than that. Never. Ever. Not in ANY ambient temperature. It's actually worse in the winter than in the summer. When it's hot out the radiator comes closer to warming the trans than it does in the winter.

Have you ever measured the temperature inside the radiator around the transmission cooler? I have. In the winter the coolant temp around the trans cooler stays cold. It doesn't matter how hot the engine is, the coolant near the trans cooler is anywhere from ~5°F to ~20°F above ambient temperature. So if it's 0°F, even with the engine warmed up and the thermostat cycling, the coolant around the trans cooler is around 5-20°F. How well is that going to warm up your trans?

And you talk about the ATF circulating through here as soon as the engine is running. That's true. How warm do you think the radiator is as the engine is warming up? It's at ambient temperature. So until the thermostat opens for the first time, which is often several miles into the drive, there is NO heat sent to the radiator. It stays at ambient temperature. So if it is 0°F outside, the radiator is at 0°F. How would it get hotter?

It actually does get slightly warmer before the thermostat opens. The ATF warms it a little! I've measured the ATF temperature in and out of the cooler along with coolant temp around the cooler and verified that this is how it works. You're guessing, basing it on how you want to believe that it works.

No, that is NOT true. It's nice to imagine that, but I've tested it in controlled conditions with a huge amount of instrumentation to be able to understand exactly what's happening.

THE RADIATOR NEVER HEATS THE TRANSMISSION FLUID.

I can't comment on what GM/Iszuzu did. On a Ford that would not be true.

But I also suspect you didn't have the same operating conditions on your test. The same load, the same speed, the same wind, the same ambient conditions, the same sun load, etc. I did when I ran back to back tests. We ran the tests in a controlled wind tunnel, and verified the results in the deserts of Arizona and California.