I've been having a problem with my 1994 F-150 XLT while driving down the road I have to turn off the O/D then turn it back on when I hit highway speeds. The issue is even more weird when I turn on my headlights it turns my O/D back on. I have checked my grounds to be sure they are good(which they are). Never essn this before.

 

Your problem is most likely associated with your tail lights or your trailer light plug-in. Installed any LEDs lately?

 

No, no led lights installed. I checked all the ground wires also