I have a 2006 Ram 2500 with diesel power and a 5 speed auto trans. 123,000 miles. The truck is like new and has been maintained endlessly. I have noticed since moving to Idaho and pulling long, steep, and winding grades pulling my 8000 lb camp trailer ( yesterdays grade was 7 miles ) about 3/4 the way up the transmission will start dropping from 2nd gear to 3rd then quickly to 4th at a speed of about 20 mph. At this point the speed will slow and when I give it additional throttle the trans will then kick up to 2nd but when the speed increases a small amount I go thru the same process. This happens regardless if I am in normal or towing mode. Sure does not seem normal and sinse it starts to happen after extended pulling up steep grades it makes me worry. Any help is appreciated.