You must have noticed something unusual in the truck because you never noticed anything wrong before. Upshifts as well as downshifts have to do with the opening of the throttle (throttle pressure cable), the speed at which the outputshaft is turning (governor pressure), and the valves located in the valve body. Only the cable is adjustable.
If it only occured once. Leave it. If you were in overdrive and it didn't downshift then it could be electrical and probably stored a code in the PCM. I hope that helps you in deciding how to determine what action you should or should not take. Joe
Friday, December 18th, 2020 AT 10:34 AM
(Merged)