@Shawn327 the circumfence is only relevant for the speedo and odometer. The transmission works with some sort of mappings based on calculated engine load/calculated torque requirement, and decides based on that when to shift up/down. You will need to modify the ECM and TCM software for a different shifting behavior.
Another thing you should keep in mind is, that much bigger circumfence means more torque needed to get the car moving under all driving circumstances. This results in much higher mechanical stress to the whole drivetrain under all driving conditions. Especially your angle gear and transmission are facing a higher torque load whenever you accelerate. Expect that you need to service or even rebuild them in the very near future. You should at least flush the transmission, angle gear, differentials and Haldex at a very regular and short interval.
