Hey guys I have a 2000 F350 dually with a 4r100 and on a recent trip to my son's baseball tournament I noticed the overdrive on light blinking so when I pulled up forscan the TFT was 273°!!! I pulled over to let it cool down but after driving for a while the temps started getting high again. This transmission was rebuilt probably around 7 years ago but I really never tow anything with this truck. The radiator is probably around 6 years old and I also installed a 6.0 trans cooler, I replaced the condenser about a year ago when I replaced my whole AC system, and I am running mobile one full synthetic ATF. The truck was still running completely fine but just wanted to see what you guys thought could be the culprit. Was going to do a full Mark k flush but there is obviously a restriction somewhere. Is it most likely the filter inside of the transmission that is getting plugged up? Everything else is pretty new aside from the two lines that go to and from the radiator / cooler. I ordered the parts to rebuild the bypass relief valve but after getting under the truck I realized that the previous owner had already deleted the bypass tube so I'm assuming that takes that out of the equation. I am going to replace the tube once I figure out what is going on. I do know that the guy that rebuilt my transmission put some kind of kit in that allows the torque converter to get a 100% of the fluid instead of sharing it if that makes any sense. Maybe that's why the transmission is not fried. I will say that I have the same transmission that was rebuilt by the same guy in my 2000 f-450 and I told very heavy with it everyday with zero problems.. Any advice on where to start would be great

 

Might need to drop the pan and see what's in it. What color is the fluid now?

What code does forscan give you for that blinking OD light?

 

173 F or 173 C?

173 F is completely normal and well within the operating range. 340 F - not so much.

Why was the light flashing? What is the code?

 

I can't remember what the code is but when I looked it up it said higher than normal fluid temp. I changed the original post but it was supposed to say 273f

 

Sorry that was supposed to say 273 f. This happened about a week ago so I can't remember what the code was but forscan said it was higher than normal fluid temp

 

Oh, yes, BIG Difference.

I am unsure of what would cause that temperature other than a torque converter clutch not applying, cooler flow blockage, or an internal friction element slipping (I would expect a P1728 at that point though and some harsh shifts). Do you have a "winterfront" installed and forgot to remove it in higher ambient temps? I assume this was occurring at highway speed.

 

https://youtube.com/@jasonmoore7322?si=3RFR7YQOS2cWjYup
I went and picked up the truck and after about 5 or 10 minutes of driving I noticed the overdrive light was blinking again and the TCC gauge was flipping out. Here is a link to watch the video, sorry it's so shaky. I'm not real sure how to read the TCC gauge or the TC slip_a gauge. Also have attached a photo of the code that is coming up for the transmission. I am in Florida so there is no weather shield on the front of the truck and win this was originally started happening I was going about 85 miles per hour on the interstate. Today I was just driving around town and it started happening again. Let me know what you think, thank you

 

If your gauges are to be trusted, your TCC slip in 4th should be 0 (+/- 10)....not 90-200.

Also, why in creation is the TCC apply duty cycle bouncing from 0-50-100 all the time?

I'd remove the flexplate cover and see if the paint's burned off of the face of the converter.

I still don't know why there's no P1728.

200-300 RPM slippage in 3rd regardless of TCC DC% is bad. As soon as the DC% hits 60% or more, slippage should be ZERO.

 

Maybe it is the tune that I am using? I will try a different tune later today to see if the gauges are going all caddy wampus. None of this makes sense. I will pull the flex plate cover off and let you know what I find, thank you for your help.

 

Is the transmission hot?? Use a non contact temp gun on the pan and see what it reads if you don't have an auxillary gauge. Is the transmission functioning normall with all gears and TCC lockup? 273* no towing just driving around is very hot especially with 6.0 cooler and Mobil 1 fluid.

 

Rather than take the bypass valve out of the equation, the missing bypass tube becomes central to the equation.

"No bypass tube" + "restriction somewhere" in the two old "lines that go to and from the radiator / cooler" = no alternative flow path back to transmission if cooler passages are restricted = insufficient return fluid flow to transmission sump = "Transmission Overtemperature Condition"

To test for any restriction in the external cooling lines and transmission coolers, disconnect the rear most cooling return line from the transmission case, and position this line in a clear container (preferably a gallon or larger, unless you have a companion that can start stop the engine for you).

This clear container should be marked in 1 quart increments, like a graduated beaker, so that flow can be measured in real time, with a watch, while the engine is running. For the 4R100, the return flow at idle is specified to be 1 gallon per minute, which breaks down to 1 quart every 15 seconds, if memory serves correctly. Since my memory is failing, I'm going to tag @Mark Kovalsky to fact check this return flow spec.

If you find that your return flow through all of your external lines and coolers is LESS than 1 quart every 15 seconds, then you have solved the equation.

 

That is correct.

 

Thank you Y2K, I will try this next. I took the truck out for a short ride yesterday and even though the truck seemed to drive normal my TCC slip gauge was bouncing all over the place again and my overdrive light started blinking. The codes that I posted below are from the previous trip, some of those codes are not relative because I have deleted the exhaust back pressure valve. I am not sure why I am getting a restriction on the exhaust as this truck does not have a cat, unless the muffler is somehow plugged up. During this short ride the fluid temp s were not hot. I am wondering if it is a tuner / PCM issue. Unfortunately since I have 160CC single shot injectors I do not have the ability to run the truck without the tuner. Cody also asked me to take a look at the paint on the torque converter to see if it is pealing off and it looks completely normal to me

 

I do not see any burned paint. You can drive the pickup without the proper tuning for the single shot injectors, it will just have a very touchy accelerator pedal. It's a good place to start with diagnostics.

 

Okay I will try to figure out how to disconnect the Hydra and see if the gauges still jump all over the place