While driving down a curving mountain highway above 70 mph, the gauge cluster displayed “shift to park” or “shift to drive” I don’t recall exactly. The transmission then downshifted dramatically, perhaps into 3rd gear, then the motor shut off.Thankfully, I successfully merged through heavy traffic to the narrow shoulder but the truck would not restart. After over 30 minutes of attempts (fuel tank above half)I called a tow truck. My family climbed up the hill to get a safe distance from the road. It was cold and dark and things could have gone much worse. Ram owners on internet forums have described this exact problem many times and it’s clear that this is a wide spread safety issue. This is the second time the truck had lost power while driving in the same manner. The first time the dealer could not replicate the issue while it was under warranty and returned it to service. No I’m out of warranty, need a new transmission at largely my own expense and there are zero available in the country. The dealer has my truck for an “indefinite” time period.