I have a 2011 2500. I tow most every day and have had the trans serviced 2 times in 109,000 miles. It has always searched for gears when it's cold and the dealer said that's normal for some trucks. Now it struggles to downshift at 45 mph and wil search up and down repeatedly until I stab the gas to get it to downshift. I had a local shop look at it and they did a quick learn on the trans . It was fine for 500 miles now it's back. Ant ideas.? To me it seems like a sensor issue