The band-aid tires are your problem. Get some 16" wheels and tires with real sidewalls and increase the rolling diameter, and your problems will go away. The Ram 1500 I use on business had the opposite problem- - - -the 17" wheels and tires that were on it when I bought it made the cruise speed "sweet spot" about 75 MPH. When I tried to cruse at legal speeds on the interstate, the transmission would constantly toggle in and out of torque converter lockup, and it would occasionally drop out of overdrive into direct. The solution was to install 16" wheels with 70-profile tires to drop the road speed at 2K RPM where the engine likes to run. It resulted in a 5 MPH error in the speedometer according to my GPS, and nearly a 2 MPG improvement in gas mileage because the engine quit lugging down and opening up the full power calibration of the computer controlling the injectors.
Your situation is different- - - - -you need a taller tire and bigger wheels to give you more road speed for a particular RPM.
Jerry
