I have a 2007 SR5, 4.7 with tow package. My issue is today for the 1st time my trans temp gauge red lined. I just went up a incline of two mile at 7% grade and was home. I was backing up my trailer (which has a dry weight of 5600 lbs. and Gross weight of 7600 lbs. But I never travel with fluids in my trailer so I would be well below the max weight for towing. I have towed this trailer over mountains and no issue. Just had my truck's cooling system flushed and replaced at the dealership. Outside temp was around 74 degrees. I ran my transmission in "S" mode at 4th gear and it kept kicking up and down the different gears. Related? I don't know. Could this just be a fluke? I feel that the truck can more than handle this tow job.