One of the things I don't like about my SuperDuty is when in tow/haul, or if the exhaust brake is on, if you apply the brakes it shifts down. For this reason I will use manual mode when descending hills and choose the gears myself. This allows me to use the brakes sparingly if needed without reving too high. OP, good for you getting it checked since the warning lights came on, but I doubt you damaged anything. These newer trucks computers usually keep them from harm. One other thing, If I recall, the trucks with "Hill descent control" are designed to use cruise control for setting downhill speeds. Does your truck have that option? Might be something else to check. Good luck.
