New oil cooler, new EGR cooler, new EGR valve, new injector harness, new filters everywhere, EL Red coolant, T6 syn oil. 8000 lb. trailer pulling a fair hill. Truck is not in haul/tow but is doing OK. It decides it needs to down shift and when it does, within seconds the wrench appears. Scan II gauge does not show that the turbo boost is excessive - probably about 19 or 20.
This is the same event that started the repair/replacement thru' out the winter. I'm starting to lean in the direction of a turbo problem. Over boost? Under boost? Thoughts from the experts please. Temps were fine. Never more than 8 degree difference. Also, got to the top of the hill. Turned it off and then right back on. Wrench was gone. Drove 20 miles home (in tow/haul) without an event.

 

You need to get it code scanned to see what code is stored to make sure.