I have a 2007 ford 150 4x4. She slips when trying to go into fourth gear when over drive is on. Just like many other cases here, it drives prefect with overdrive off.

I took apart the main control valve body. Everything looks good. all the clips and rings seem to be fine. The fluid is dark reddish. There was a very small amount of shavings in the pan, maybe a finger nail sized amount.

There was nothing around the magnet. Havent checked the overdrive band yet tho.

Thoughts?

 

Did you check the wear in the OD servo bore. There is a servo oin kit for it.