The speed sensor on a 1996 Dodge Dakota is located in the
differential. More specifically, it's usually on the
passenger side of the rear differential housing. However, there's a small chance it could be on the driver's side depending on the specific options and configuration of your truck.
To be certain, you'll need to consult a repair manual specific to your 1996 Dodge Dakota's year, model, and engine. A diagram showing the sensor location would be the most helpful. You can often find these manuals online or at auto parts stores.