Rear Differntial Clicking Noise

[ToboJosh]

I have been hearing a clicking noise coming from what sounds like my rear differential. The noise is very random and doesn't happen every time I drive. When the clicking noise does happen, I am going between 5-15 mph. I have been experiencing RPM surges when I hit a bump in the road while cruising at highway speeds (65-75 mph). The truck has 160,000 miles on it and I bought it 3 years ago with 105,000 miles. I have never had the differential fluid changed. What could possibly be the culprit and is there anything I can do to fix the problem?

 

[hotkarl]

Somehow, you need to verify if it is indeed coming from the differential.
Could be anything, springs, shocks, brakes, any number of things.