The speed sensor on a 2003 Chrysler Town & Country is located within the
transmission. It's not externally accessible without removing the transmission. There are actually two speed sensors, often called the Vehicle Speed Sensor (VSS) and the Output Speed Sensor (OSS). The exact location of each within the transmission varies slightly depending on the specific transmission type (e.g., 3-speed automatic, 4-speed automatic).
Therefore, you'll need a repair manual specific to your 2003 Town & Country's transmission type to pinpoint the exact location. Trying to find it without one is highly discouraged, as you'll risk damaging the transmission.