From what I have found researching and owners manual, it states replace transmission filter and fluid at 150K. Dealer told me I need to service the transmission at 30K. I have 32K on the truck. It's a daily driver and I tow loaded around 15.5K lbs 5th wheel about 8 times a year.. Most trips include mountain grades. Also tow 6K lbs boat several times a year. What is the "normal" needed transmission service interval for a 350 dually? is the owners manual 150K ok? That sounds extreme and I was thinking unless having issues 1st service on the transmission at 60k.