I having problems with the old dodge. When driving around 45mph the trans is confused shifts up then down up an down up an down. If pulling a load it is a lot better, and doesn't miss a beat when under full Throttle.

Does this sound like the Throttle Position Sensor. if so where is it located and does it need to be removed to clean.

 

Check your brake light switch. Take the truck out for a drive and when it starts jumping between gears put the toe of your boot underneath the brake pedal and hold the pedal up. If it stops jumping around there is some play in the pedal/switch setup and the brake light switch is kicking the trans out of OD. You can either adjust the switch or replace it. If that doesn't work it could be the TPS. PM with questions...

 

clean your battery terminals and any grounds you can see that are dirty. This fixed mine. And it was doing exactly the same thing.

 

45 is the exact speed mine would shift from 4th to OD. I just always drove either 50+mph or -45mph. i didn't notice my truck going out of OD, but when it went into OD u can feel the TC lock up for sure. So all I can say is drive alittle faster or alittle slower, lol.