94 f150 302 4R70W
Hi folks, on 4 different occasions, my truck has downshifted on the eway for no reason. I let off the gas it upshifts immediately and all is fine. No flashing lights other than airbag. All fluids changed 5k miles ago. PSOM taken from my 5 speed. Alls been good for months.

 

So you were cruising along on level ground at moderate speed(ie light throttle input) and the trans downshifted? Regardless you need to pull codes and post up what you find.

 

Conan is right, the computer will store a code if some error occurs and not turn on the check engine light, I have actually never seen mine illuminate while running in the 5 years I've owned it. It always stores the code (if one occurs) in continuous memory.

 

Yep. Downshift, it was light throttle, about half a toe's worth,lol. We're not talking unlocking the torque converter- its downshifting to about 3500 rpm on the highway.
. Pulling codes is always a good thing. But, it was my understanding that the engine and trans are 2 separate systems.

 

You are mistaken.

The same computer controls the engine and transmission. That is why it is called the Powertrain Control Module.