Nice truck, does it have the 5.9 or the 6.7?
Drive it smart and the transmission will be fine. For instance, don't hot rod it from stop light to stop light, especially not when you've got a load behind it, combined with the larger tires you've already added. Anytime you add larger tires you add stress to the drivetrain. Extra stress on the drivetrain is going to shorten the life of parts, particularly the transmission, and it'll effect any manufacturer, Ford, Chevy, or Dodge. In stock form either automatic that was offered behind those two engines during which ever model year your truck is, will be very reliable in stock form. But, like I said, if you start getting stupid with it then any truck will break on you. Take care of it and it will treat you well. The Cummins Dodge is a highly reliable and capable truck.
agreed, I have a friend with one and he just tuned it and added quadzilla and bam he had to get a new transmission
It's amazing how many people blame the manufacturer when the transmission breaks because they've add more power to the engine and the transmission was built to only handle stock engine power levels in the first place.