Originally Posted by JCL

We could do an easy test here. You could drive your car off a cliff. As you plummetted towards the ground, take your foot off the gas, and check your speedometer. If I am right, the speedometer will be zero. If you are right your speedometer will function as an airspeed indicator, indicating your velocity up to terminal velocity. If you want to reduce the damage potential then you can skip the cliff-jumping part. Just spin your tires in the snow. You won't go forward. Using accelerometers, the speedometer would show zero. I suspect you will find that spinning tires results in a rising speedometer reading. Let's just assume that if the transmission knows vehicle speed then that is what it is indicating on the speedometer.
JCL