Wrench light and overdrive issues

[csuexplorer]

2006 explorer with v6 4x4 on long highway trips the transmission will shift down to fifth gear for no apparent reason and not shift back. Shortly after that happens the wrench light comes on. If i stop the vehical and restart the car all is fine for a short period of time and then it reoccurs. No codes on my basic scanner. Any help would be appreciated

thank you

 

[JK080]

Your definitely going to need a scanner that can read transmission codes. Thats the first place to start.