*Again, a mechanical speedo does not have any affect on an automatic transmission. As jerrod re-stated in this thread, the speed sensor is what talks to the ECM and Transmission ECU. Trust me here, unless the right side tailshaft of your truck has an electrical output for your speedometer, it doesn't talk, it spins a cable going up to your speedometer. The speed sensor is a completely different unit in and of itself.
kcndc...
READ ME! so you understand things.