According to the manual, my truck can pull a 9100 lb load behind it, but I was pulling a 1500 lb trailer and a 5500 lb Jeep on it over the last week through Colorado from Kansas and the transmission was heating up, then coming down the other side of the mountain, the engine overheated to the point that it went into safety mode. I watched the transmission temperature constantly, but it wasn't until it went into the safety limp mode, did I set up the meter to also watch the real time engine temp. The temperature would stay cool going up the mountain, but using the engine as a brake coming down the other side the engine heated up quite high.
We pulled over to cool it back down multiple times, but it would heat up again at the next opportunity. We went to a car wash and blew a bunch of junk out of the radiator, and that seemed to help a bunch. It was the middle of the night so outside temps were cool, and we made it to Utah fine. We felt like things were going well, until we were headed back through Utah, I was descending a mountain, and the engine temperature was climbing. It was a casual descent, so I put it up in neutral for about a mile. The temperature kept raising higher and higher, so I revved the engine to help the fan run harder. This didn't help. I eventually had to pull over and shut it down, because setting on the side of the road idling still caused the temperature to climb. I let it cool off good then hit the road again, at which seemed to work fine with no temperature issues. When we arrived to our Colorado Destination and I unloaded the Jeep, and took it to Oreillys for parts in a separate town. I bought a new fan clutch and new thermostat and installed them. The engine temperature stayed nice and cool like I hoped the rest of the way home. The transmission temp sneaked up a couple of times, but we quickly pulled over and let it cool down again.
Finally to my question...
In addition to the stock transmission cooler, what aftermarket cooler do you recommend for maximum cooling? Do you also recommend an electric fan on the cooler as well?

 

I'd also consider a new water pump. When was the last time the transmission fluid and filter was changed? Does the radiator need to replaced? It could be some of the parts are wore out or occluded. I would make sure the original parts are in good working order before upping the ante with an aftermarket cooler or electric fans.

 

In addition to the above, did you check your coolant levels and verifiy you were not running dry.

What about the fan shroud? Still intact as built when new?

You can search online for aftermarket coolers and setups but they may or may not help.

When you say overheat what were those temps for the engine and transmission?

 

So the truck has just around 90,000 miles on it, the fluid levels were perfect before and after this occurrence. As far as the engine temperature, it is fine now that we replaced the fan clutch and the thermostat. After replacing the fan clutch, I could hear the fan howl at times, I had not previously heard this since I owned the pickup. (4-6 months) Also there was a distinct temperature drop when the thermostat opened, which wasn't the case before. The fan shroud is just like brand new, as is all most all of the truck, the previous owner did not put many miles on it, and stored it inside, as well as took really good care of the truck.

Mostly I am concerned at this time with trying to keep the transmission temperature down while towing. Thank you for your input so far fellas!

 

The trans temperature stayed nice and cool down around 168-190 degrees, but up in the mountains I was seeing temperatures of 210-228 near the top of the mountain going up and then it got up to 231 coming down the other side at one time, but cooled down a little. I really tried to not let it get any where near that temperature, and let it cool down as soon as I could get to a pull off spot.

 

If the transmission temp climbs while towing and pulling a grade, what happens when you take it out of overdrive?

 

Gear hunting may also contribute to the higher temps.

 

I am very strict about not pulling any trailer in overdrive. On this trip there was only one time that I forgot to turn off the overdrive, for only about 5 miles, and luckily it was on a flat stretch of highway. Thank you for asking.

 

Yeah, but when it was gear hunting, I would drop it down in gears, and sometimes go down to first and back off the speed to about 10-15 miles per hour, paying close attention to where it was that the torque converter was locking in, as to try to not create more heat.

 

At highway speeds the clutch fan shouldn't need to do much. I had e-fans in my prior truck and they would rarely turn on when driving on the highway. Overheating downhill should be a huge red flag that something isn't working right. It sounds like the new thermostat was the critical change.

I had an aftermarket transmission cooler in my prior truck (Nissan Titan) and it helped. I think it was a TruCool. Check with the guys in the F-150 forum to see what they're running for your specific engine/transmission. However, you may eventually have to say that it's not just a cooling problem and your transmission is actually shot. My Titan never had an issue up until about 60,000 miles. After that I had to actively manage the gears even when pulling my side-by-side up Colorado mountain passes at 45 MPH. If I had kept it then I was going to have the transmission rebuilt by Level 10 Transmissions.

 

Thank you Jim for your time and information. I truly believe we have the engine issue resolved, its just the transmission that I want to avoid causing further issues with.

 

Adding an additional cooler shouldn't hurt anything except your wallet.

 

Yeah, I figured that it would just be a cost thing, mostly I was thinking you all might have the inside scoop on the best one to use, but I will take Jim's advice and check on the F-150 forum to see what they suggest for the best one. Thank you everyone for the thought you put into this.

 

I'm a big fan of Hayden products and have run their oil coolers on several vehicles.

https://www.haydenauto.com/ROOT-Home/Content.aspx

A basic 12-18k cooler would be all you'd ever need, if that.

Griz

 

Thank you for chiming in Griz!

I will look into those!!