My transmission started shifting erratically. It would go from 8th to 10th gear down to 1st or 2nd gear then go back to 5th while trying to merge into oncoming traffic. People had to lock up there brakes or swerve around me to avoid a collision. There were no lights on the dash. I had a transmission shop take a look and there were no failure codes for the transmission. I have had to park the truck due to safety concerns and not drive it. This happened on several occasions during that trip.