Jack Bresser

I have an '03 F150, 4.6 auto supercab 2wd that has the towing option. I tow a '05 T-Bird to Florida and back yearly from Cincinnati. The tranny seems get sluggish/overheated in the mountains. What kind of cooler should I add to help this and exactly where should I put it and pipe it? The fluid already goes through the radiator and cooler in front of the radiator.

Greg_8507

You should be able to find an aftermarket cooler that will offer far better cooling capacity than the factory cooler, and all you have to do is switch one for the other. Suncoast makes upgrade kits and packages for a lot of transmissions.

I don't know how fast you're going or wether or not you are turning O/D off, but you could try slowing down and keeping your RPMs lower and turning O/D off.

tomb1269

1st your most likely towing past your GCWR capacity. If you are using an open trailer I assume your weight must be up about 6000lbs for the car and trailer (cars is just under 3800 curb weight alone). This leaves around 5500lbs for truck, gear and people. If your caring more than 1000 lbs in people or gear your most likely over weight and thst for the 3.55 axle. If you have a 3.31 axle you loses a 1000lbs of capacity.
2nd Auto matics tend to make the most heat when they are hunting gears, i.e. shifting frequently. 2 ways to minimize this; one turn of overdrive your load is to bid to be running in overdrive. second let the trucks speed drop going up hill, you do not need to floor it and make the truck top the hill doing 65 -70, also gently pickup speedup before the base of the hill and hold steady on the throttle on the way up letting the truck slow if it needs too. If you using a closed trailer, your just way overweight and even the best driving techniques most likely will not help and neither will a cooler. You need a bigger or newer truck that has greater capacity.

jackb

I tow with a tow dolly that weighs 500lbs. The T-Bird weighs 4,200 lbs, and we probably pack 1,000lbs. I'm sure I'm towing at full capacity and turn off OD in hilly country. i also slow down in the mountains and try to respect the load I'm hauling. The only time I notice anything is in the longest grades where it's building heat. I'm really not trying to go faster, I'm just trying to get more heat out in those situations to save the tranny. i was thinking of mounting two double pass finned aluminum coolers on the frame and connecting one through the supply and one through the return while continuing to use the factory coolers. What do you think???

This truck tows very good and averages 12.5 mpg which I am very happy with. I just don't want to destroy my nice truck.

willieboy

To me, it sounds like the truck should be able to handle that load without too much overheating. I am thinking your torque convertor might be showing it age and is slipping excessively when under load. That will cause A LOT of heat. The problem with adding more tranny coolers is that too cool of fluid is not good for a tranny either. So for those cases where you are not towing in the mountains, the coolers maybe too efficient and cause harm that way. The one options I would consider is adding an auxillary electric fan to the existing tranny cooler. You could turn it off and on when needed. You should also add a tranny temp guage, and measure the fluid at the point it is exiting the trans, before it enters the radiator or secondary cooler. That way you will know when to turn the fan on or off. You could also have a themostat to control the fan if you wished. All that said, I would get a good transmission shop to do a good check on the trans. It could be the torque convertor, or even a valve body that needs serviced.

smokeywren

I owned a 2003 F-150 Lariat SuperCrew 4.6L with 3.55 axle for about a year. It simply wasn't enough truck for my needs. Mine didn't have the trailer tow pkg, but I had my dealer add the oil-to-air (OTA) tranny cooler before I towed a 7x14 cargo trailer to Phoenix and back. Loaded trailer grossing about 6,000 pounds from Midland to Phoenix, the truck was loaded to the GCWR. It made it, but it wasn't happy. On the return leg with the empty trailer, it was still not happy. Apparently, wind resistance was a bigger factor than trailer weight. There are a lot of long steep grades on that road that you don't notice when not towing. So that trip convinced me it was time to trade for a more-powerful truck.

I'm still not much of an expert on the F-150. But I owned an F-250 PowerStroke diesel for over 11 years, and spent a lot of time on TheDieselStop as a contributor and moderator. From 1995 until 2003, the 7.3L diesel with automatic tranny didn't have enough tranny cooling capacity for serious towing in mountains. The fix was to add a big OTA heat exchanger with a fan under the truck. The fan was controlled by a thermostat installed in the cooler return line. If the cooled ATF was over 180°, then the fan came on to further cool the returning ATF.

Later Ford came out with a much bigger OTA tranny cooler for the 6.0L diesel. Today the fix for the 7.3L is to replace the smaller OTA cooler with the much bigger OTA cooler from a 6.0L diesel. It's a bolt-on replacement, and works almost as good as the big cooler under the truck with a thermostatically controlled fan.

If you primary objective is a cooler tranny when towing, then first I would do some precise measuring where the current OTA cooler is installed to see if you can install a bigger OTA cooler to replace the current cooler in that area. If not, then you have your work cut out for you by fabricating hangers of some sort to mount a big OTA cooler with fan under the truck. You can control the fan with either an on/off switch, or with an automagic thermostatically controlled switch. I would use the thermostat, installed in the cooler return line and set to turn on the fan at anywhere between 180° to 200°.

The following link was the most popular combo for increasing tranny cooling capacity on my '99.5 PowerStroke. Notice there are optional wiring kits and mounting kits available that might save you some frustration in installing such a cooler under the truck.

Perma-Cool tranny cooler with thermostat controlled fan

WARNING: You have to do an excellent job of plumbing so you don't kink a line or screw up a connection and reduce the flow of ATF through the tranny cooling system. After you get done, then do a flow test to be sure you still have enough flow through the coolers. I don't know the specs for your tranny, but for the 4R100 tranny in the '99-'03 SuperDuty, it was one gallon per minute, or one quart in 15 seconds, measured at the place where the return line goes back into the tranny.

jackb

I've learned a lot from the posts that have been made to this question about my F150. I think my best move right now would be to replace the finned cooler in front of the radiator with a larger one that has a thermostat controlled fan to help cool under heavy loads. Thank you to everyone who responded to the problem. I will post results after we pull the car home in may. Jackb

jackb

It's getting about time to tow the T-Bird back to ky so I did install a B&M cast aluminum finned deep tranny pan. It holds three extra quarts of fluid.
When we get home I'll post an update if that alone was enough to fix the overheating tranny in the mountains.
The fluid I drained out was not burnt, it looked and smelled as good as the new that went in. That tells me there was no damage done to the tranny. jackb

smokeywren

According to Mark Kovalsky, a Ford tranny developmental engineer for about 20 years, the tranny pans with more capacity do NOT provide any extra cooling. For short trips, they do require longer to heat up the extra ATF to the too-hot stage, so that may be all you need to get you over the pass before the tranny gets too hot.

But then after the ATF in the pan is too hot, it takes a lot longer for it to cool down to operating temp.

So you still have to have a good tranny temp gauge that tells you sump temp, and 225° is still the red line. With the bigger pan, when you get up to over 220°, you still have to stop and put the tranny in park or neutral and elevate the idle RPM to about 1200 to 1300 RPM, so the tranny pump will pump ATF through the coolers, and the engine fan will continue to suck the heat out of the ATF as it passes through the heat exchanger(s). With the extra hot ATF in the pan, it will take longer for the tranny temp to fall down below 210°.

The only fix for inadequate tranny cooling is a bigger heat exchanger, or a fan that pulls more air through the heat exchanger, or both.

The stock engine fan on my '99.5 PowerStroke was a really strong fan that worked great when the air coming through the radiator got up to 200° and locked the engine fan "on". That fan used 27 HP at full song, and it forced a hurricane worth of air through the radiator and tranny cooler, so they cooled down "right now". But the tranny could get too hot before the coolant in the radiator got up to 200°, and there was no way to turn on that stock fan until the thermostat in the fan saw 200°. It was a viscous fan, so it pulled some air through the radiator when not locked, but not enough to quickly cool down an overheated engine or tranny. So my first fix was to install a Cyclone engine fan that was controlled by a thermostat in the cooler return line. When the returning cooled ATF was over 180°, the engine fan would lock on and it would immediately cool off the tranny temp. Worked great except the senders had to be replaced frequently. But U.S.Gear stopped selling the Cyclone after I bought mine, so others had to find some other way to increase tranny cooling.

jackb

I took the advice of smokeywren and installed a 24" duel pass aluminum cooler along the outside of the frame. I piped it up with 5/16 od copper tubing and hopefully this will do the trick along with the deeper finned pan. I'll post a blog when we get back to ky.