Help save your tranny, use cruise control.
 

I have a gryphon programmer and noticed that whenever I am at interstate speeds and let off the gas the torque converter unlocks.

As soon as I touch the pedal again it locks back up.

It doesnt matter if your going downhill or on flat land it always unlocks upon releasing the throttle.

when u use cruise control it always stays locked unless you actually need 4th.

So use cruise control to avoid a ton of unnecesary shifting between 4th and OD.

Interesting, I have notice better engine braking in cruise VS. cruise off and that may be why. I guess it is to allow coasting with little resistance to save gas. I am curious though I did not know Ford installed 4 speed autos with overdrive in 04-08 F150's I thought they were all 3 speed with overdrive, I wish I could swap one into my 04 (though the 3 speed I have does not have any problems) the extra gear I think would make acceleration smoother