Clint - I'll leave you with this and if you do this read and still don't understand it's beyond "communication". You need to pay attention to R1 and R2 explanations and maybe it will make better sense to you. Limit your thoughts to "drive-shaft" revolutions which don't change until the axle ratio and tire diameter becomes involved.
http://wahiduddin.net/calc/calc_speed_rpm.htm
Unfortunately every time that axle ratios get involved the formula seems to relate to end MPH and the transmission only controls drive-shaft revolution. Use the calculator that I linked to and use any RPM and change only the rear axle ratio and it will be displayed in a graph and also print. There are several other calculators that do the same thing but don't display the results in an easily understood way to be compared.
If you use my linked calculator and keep the RPM involved at an even thousand it's much easier to compare the MPH effected by the axle ratio and tire dimension. Use 5000 or 6000 or 7000 RPM, change the tire dimension and change the axle ratio to as many variables as you like and I believe you'll see the RPM differential didn't change but MPH changed only in regard to axle ratio and wheel dimensions.