The industry standard for the speedometer cable is 1000 rpm @ 60 mph. So since 60 mph covers a mile in a minute the speedometer cable spins 1000 times per mile.

I like your idea of the speed sensor controller. Even though the use of pressure switches SEEMS simpler, the use of a bunch of mechanical devices almost guarantees that the system will fail at some point. Also, the issue of line pressure has to be addressed. Maybe that shift kit I just bought increases line pressure all the time. Now I have to buy new pressure switches or adjust and calibrate the old ones if that's possible. Contrast that to a stationary sensor counting teeth. Either it works or it doesn't and if it doesn't you replace the sensor which costs $20. At least the sensor in my 4L80E cost that when it went out after 130K miles.

I'm a mechanical engineer and I'm changing out some 50-year-old mechanical governors for digital in our hydro plant, because there are some things that digital just does better.

R.