I put in 80 mph x 4.10 x 336 / 25.5in = 4322 RPM's. That would most likely be 3rd gear right? I want to make sure that this is right because it could help a lot of people.
I got this calculation from a guy who wants to put gears in his Dodge Ram. He is going with 4.56's. I'm not sure if this calculation works for only Dodge Transmission's.
TireRevsPerMile can typically be found on the tire specifications sheets. It's a better term to use than the diameter because it represents the real-world, loaded and pressurized effective rolling diameter of the tire.