how can i locate the two in & out transmisson speed sensors on the transmission?

Input Shaft (Mainshaft) Speed Sensor Replacement Remove the intake air duct and air cleaner housing. Disconnect the input shaft (mainshaft) speed sensor connector, and remove the input shaft (mainshaft) speed sensor. Install the new O-ring (A) on the new input shaft (mainshaft) speed sensor (B), then install the input shaft (mainshaft) speed sensor in the transmission housing. Check the connector for rust, dirt, or oil, and clean if necessary, then connect the connector securely. Install the intake air duct and air cleaner housing. Output Shaft (Countershaft) Speed Sensor Replacement Remove the air cleaner. Disconnect the output shaft (countershaft) speed sensor connector (A). Remove the output shaft (countershaft) speed sensor (B). Install the sensor in the reverse order of removal with a new O-ring (C). why do you think they need to be replaced?? the odd of both of them failing at the same time are remote. Roy