Speedometer Not Working

[JMan300sd]

Hello all! My Speedometer recently quit on me. My odometer still works though. I have no idea where to start in terms of fixing this issue. After doing a few searches Ive learned that on the SD it is electrically controlled with a sender unit from the Tranny. What Ive read is that the sender unit rarely goes bad, but then where do I look? Any help at all would be greatly appreciated.

Thanks