It sounds like you have a shift solenoid that is not working. I would test through the winding's to see if there is continuity. Also, check the four fuses that run the system. You can see which ones from the diagram below.
Here is a guide to help us get started:
Also, there is a ranger selector switch I would test as well.
Here is the transmission wiring diagrams so you can get started.
Check out the diagrams (below).
Please let us know what happens.
Images (Click to enlarge)
Saturday, February 17th, 2018 AT 11:48 AM