The tranny is whining. Sounds like the typical power steering pump whine but it is not. It is constant and increases and decreases in pitch with motor speed. I believe it to be the pump in the transmission. Could there be other causes? It seems to function just fine and there is no discoloration or smell to the fluid. The truck has 80,000 miles. Not a lot of money to spend but was thinking replace only the pump and put it back in service instead of waiting for it to fail and be committed to a full rebuild. Opinions welcomed.