However, it's not always in the same exact spot on every vehicle. Some slight variations in placement exist due to differences in options and manufacturing tolerances.
To be certain, you should:
1. Consult a repair manual specific to your 1998 Dodge Ram 1500 5.9L. A Haynes or Chilton manual will have diagrams showing the exact location.
2. Use a reliable online parts diagram. Many auto parts websites allow you to select your vehicle's year, make, model, and engine to view diagrams showing the sensor's location.
Looking at the rear differential with the wheels on the ground should be your starting point. The sensor is usually magnetic and attached with a couple of bolts. Be cautious when looking around the differential as it is usually greasy and potentially hot if the vehicle has been recently driven.