There isn't a single "input transmission speed sensor" in the way some vehicles have a dedicated sensor for that specific function on an automatic transmission. The 2001 Oldsmobile Alero's automatic transmission speed is typically derived from the
output speed sensor, sometimes also called the vehicle speed sensor (VSS). This sensor doesn't directly measure input shaft speed, but rather the speed of the output shaft connected to the wheels. The transmission control module (TCM) then uses this information, along with other inputs, to calculate the input shaft speed indirectly.
Therefore, you won't find an "input transmission speed sensor". The output speed sensor (VSS) is the key component involved in determining the transmission speed. Its location is usually on the transmission case itself, near the differential. It's often a small, magnetic sensor with a single wire connected. You might need to look underneath the vehicle to locate it. A repair manual specific to your 2001 Oldsmobile Alero will show the exact location with diagrams and images.
