If the tachometer shows an RPM reading but the speedometer does not, what could it indicate?

The indication that the tachometer shows a reading while the speedometer does not often signals a potential issue with the transmission system, particularly regarding the gear selection. When the engine is operating, the tachometer reflects the engine's revolutions per minute (RPM). If the vehicle is not moving or the speedometer is inactive, it suggests that the vehicle is not conveying power to the wheels effectively. This can happen if the transmission is inappropriately engaged, such as being stuck in neutral or in a gear that doesn’t allow for proper acceleration. Therefore, having a functioning tachometer alongside a non-operational speedometer can highlight problems related to transmission engagement or other mechanical issues affecting the vehicle's ability to convert engine power into forward motion.