It sounds like you have an overdrive shift solenoid that is not working. Here is the transmission wiring diagrams to help you see how the system works and the valve body showing the solenoid. I would change out the one with the blue wire going to it. Check out the diagrams (below). Please let us know what happens.
Images (Click to enlarge)
Friday, November 2nd, 2018 AT 12:20 PM