2004 f350 6.0 diesel- tow haul light flashing sets stuck in tow haul and wont shift to overdrive

NEED TO SCANN THE VEHICLE

lock up torque converter is toast. I had the exact same problem in my 2003 2500.

That light means that the shift points have changed on the transmission. This is to get better economy when hauling. If it wont stop flashing then there is a valve in the transmission that is bad or sticking. You will have to have it removed and overhauled..

That is the Tow/Haul indicator. Button on the end of shift selector was most likely depressed during shift or possibly a malfunction with the tow/haul mode selection system. (IE: Tow/Haul button)

you have a major problem in the transmission, take it to a shop

You either have a bad switch or the wires have lost contact.
The tow/haul switch is part of the shift lever and is not replaceable without changing the shift lever. The electrical connector is located inside the steering column covers. These wires have been known to part.

Taking a guess at it, I would have to say that the transmission fluid is thermally broke down from the heat, and stress from towing. Try to change transmission fluid and filter. If this does not fix it the transmission itself may be damaged from the excessive strain, and heat. (heat is number one cause for transmission failure. After this problem is fixed, next time NEVER tow in Overdrive. This over works the transmission, and creates the excessive heat. If you tow a lot than consider adding an after market transmission cooler. Which is only approximately 100 and up, but will save thousands in the long run:)

Is your tow/haul button on? If not, it could be activated erroneously. It'll keep it from shifting into overdrive and locking the torque converter, and also keeps the transmission from shifting more often. If this isn't the issue, then you'll have to look into your computer, as the transmission shifting is controlled by the computer. The transmissions were the weak points on these trucks; only good for max 200000 miles, so if you're getting close, keep that in mind.

on your dash console above your gauge`s where your check engine light and etc. it will say tow mode ON or tow mode OFF when you push the button on the end of the gear sellector .

Check your tow/haul switch and see if it is stuck. May have to use diagnostics to see it. Unfortunately this would be dealer level diagnostics...