The ABS rear speed sensor on a 1996 Chevrolet Tahoe is located
on the top of the differential housing, near the axle shaft. There's usually one sensor for each rear wheel. To be precise, you'll need to locate it on the
differential cover itself. It's a small, cylindrical sensor that typically has a single wire connected to it. You might need to consult a repair manual or a diagram specific to your year and model to pinpoint the exact location on the differential.
Important Note: Access can be limited, and you may need to remove parts such as a skid plate or lift the vehicle to reach it.