Ok, I'm at a loss! I'm hoping Master Mark or someone can help me solve my trans temp problems. It's a 2004 F250 V10 4x4 with the 4R100. I'm the original owner and have towed various trailers over significant grades without the trans ever heating up. I always relied on the trans temp gauge that is included in the instrument cluster. Now 2.5 years ago I lost my trans, because (I believe it's called) the sun gear split. I had a reputable trans shop rebuild it and I was good to go. 1 year later I was traveling over a significant grade that we have here in southern CA called the grapevine and I was doing so without towing. Halfway up the grade my trans temp gauge hit the red area and my overdrive light started flashing. I took it back to the trans shop and they hooked whatever meter they have up to it a drove it. They said that the trans was running at 100% efficiency, so I figured I had cooling issues. Around town it wasn't overheating too bad, so I just drove it. More recently it's been overheating on a regular basis, so I decided to find the bug and fix it. I did a flow test based off the specs someone on here said is Fords process, which said I start/run the vehicle for 15 seconds and I should get 32oz or more, and I did get more. I figure there is good oil flow, so I replaced the fan clutch and flushed the coolant system. This did not help, so I took it back to the trans shop. He's telling me that they only got it up to 205°. So I went and bought a Scangauge 2 and started monitoring it myself more accurately. Driving on the freeway 60-80mph without any significant grades, I'm reading 220-255°. It idles around 180-185°. So today I put on a second trans cooler in series after the stock cooler and mounted it in front of everything, so that it's getting the first coolest air. Surprisingly it did not change much. It was 100° outside and the trans was running 230-240°. Does anyone have an idea what could be causing it to run hot? The trans shop said the oil looks good and doesn't show sign of overheating, but Those temps are too high and if I go up a good grade, the trans temp gauge on the dash is hitting yellow. That is definitely not normal for this truck.

 

Not sure if it helps, but I have a small exhaust leak and no muffler on it right now. Also, engine water temp is 200° no matter what the trans does.

 

They made that up to make you go away. There is nothing that can hook up that says the trans is at 100% efficiency. And the trans cannot ever run at 100% efficiency, that's impossible.

That's good. Did you get fluid coming out of the trans connection where you removed the line to run this test?

I'm not surpirsed. I'm more surprised that your cooling problem didn't get worse from doing this.

A third cooler adds too much restriction to the fluid flow. This can actually reduce the amount of cooling you have.

There are two most common causes of the trans running too hot. Either not enough oil flow, or not enough air flow through the coolers.

You tested the oil flow, so that's not likely to be the problem. Is the air flow to the coolers clear? Do you have anything blocking any part of the grill? Is there debris (leaves, paper, etc.) in between coolers blocking part of the airflow? Are the fins on ANY of the coolers damaged?

 

Yes I got fluid out of the return line and not the trans where the bypass is connected. As far as I can see, there is nothing blocking airflow. The AC condenser in front has a few minor bent fins, but nothing significant. I've spayed the trans cooler, AC condenser, radiator and power steering cooler with simple green and hosed off to make sure they weren't plugged. I guess two questions: 1. Could the trans cooler need to be replaced even though there is good fluid flow? 2. Maybe the new fan clutch is faulty, but wouldn't freeway speeds provide enough airflow?

 

Also, when I say that they said the trans is running 100%, what they meant is that the converter clutch was 100% engaged and the trans wasn't causing any heat from friction.

Should I remove the new auxiliary cooler?

 

80-100° over ambient is what you should be seeing regularly. Definitely remove the extra cooler.

When you flatten out after the grade does the transmission temp come back down at all? Which Transmission fluid are you running? Frequency of fluid change?

 

I've been dealing with a similar issue this week. My truck is a 99 4wd, DRW, V10, 4R100. I was on vacation towing a 5th wheel in the Reno/Lake Tahoe area. For comparison sake I was running 220 to 240 after 30-40 minutes of towing, at which point I pulled over and let the truck idle for 15-20 minutes bringing the temp down to the 190 range, before going for another 30-40 minutes. Outside air temp was in the low 90s.

I stopped at summit racing in Reno and bought a Hayden trans cooler. My first step was to replace the stock cooler. That did not fix the issue, and made it a bit worse. After more blog surfing I found a thread

https://www.ford-trucks.com/forums/1...ucool-max.html

Of course Mark contributed to that thread also. I respect his expertise on the subject.

It seems the permanent fix according to that thread is to install a stock powerstroke 26 fin oil cooler, Ford Part number 5C3Z7A095CA. I plan to do that in the future, but to solve my immediate problem I mounted the Hayden cooler in front of the opening in the bumper in front of the condenser similar to what you did. I also took off the front license plate, which did help a bit. I have the pressure line feeding into the stock cooler, out of the stock cooler into the aftermarket cooler then to the return line, figuring, I want gravity on my side, rather than working against me. The end result was a consistent 210 degrees, never over 220 at around 95 degrees outside air temperature (while towing). I haven't driven the truck without the trailer in this configuration yet.

It seems to me you have something more going on here than I did. Your dealing with a higher outside air temperature, but I am wondering if your bypass valve is hanging up intermittently or at some point that the transmission shop is not seeing on their short test drive. You are running WAY hotter than my truck. As I understand it the valve is pressure activated and starts to bypass at 60psi. I dont know this for a fact, this is what I read on the other thread. Are you seeing a fast rise to the high temperatures? For comparison, I was seeing a very gradual rise from 165 to 210. It took about 45 minutes to make that initial climb in temperature (while towing a 5th wheel trailer, level then up grade).

Hope this comparison to a similar truck helps you. Best of luck.

 

I'm definitely over the 100° range. Today when I tested after installing the second cooler, I didn't go over any grades and reached up to 240° range. When I go over a grade it does cool down a little bit when I flatten out again, but not much. The oil was changed 30k after rebuild and haven't hit another 30k yet. It has Mercon V in it.

 

My temp doesn't rise real fast. I started it this morning and it was about 90° outside temp. Trans was 88° and drove on flat ground for 15 minutes and it got up to 205°. I wanted to put the bigger 6.0 cooler in it, but napa didn't have it in stock so I tried this aux cooler. Guess it was a waste of $.

 

@Billybob I would suggest for you to upgrade to a newer radiator with OTW cooler, our 99's didn't come with them and it will make a good difference.

Scratching head, I'm thinking something internally isn't right like Mark K said they were trying to get rid of you.

 

That's why I say I'm at a loss. I feel like the trans shop is being honest with me, but of course I have no way of knowing. They've been around a long time and they were recommended by a friend. Is there anything I can monitor with my Scangauge that with let me know if something is internally wrong?

 

Can you see between the coolers? I've seen debris collect there, blocking airflow.

I don't think so. If it passes the flow test it is working.

It should.

More correctly, when the converter clutch is locked the trans creates a lot less heat from friction. Friction never goes away.

Either that one or the stock air to oil cooler. Three coolers will have less cooling capacity than two due to flow restriction.

You can look at engine RPM compared to turbine speed RPM. They should be within 20 RPM of each other when the converter is locked.

 

Unfortunately, I can't monitor the turbine speed or input shaft speed. The only trans stuff I can monitor is 1. Trans fluid temp 2. Converter speed ratio 3. Trans gear ratio 4. Torque converter line pressure 5. Trans output shaft speed 6. Torque into torque converter

 

Converter speed ratio is engine speed divided by input speed. That will do. If it is ~1 then the converter is locked. That's what you want to look for.

Torque converter line pressure? The PCM doesn't know that, so you can't monitor it.