I have a 99 chevy 1500 with 176,000 miles on her and still going good. Ive noticed a weird humming noise under the hood, Ive checked power steering and it seems to be full but engine was warm not cold. So i will check that again soon. Then my gas gauge! I was "told" the truck had a new fuel pump put in but my Gas gauge moves when i drive then i put it in park, It moves down. What could be causing for fuel gauge to me moving?

 

Check the belt along with the idler pulley and tensioner bearings. The water pump bearing can almost cause a noise. Are you sure the fuel pump was replaced? Was the electrical connection plugged in tightly when it was changed? Check for damage to the wires going to the fuel tank.

 

The Fuel pressure regulator can also cause a humming sound.

1999 Chevrolet K1500 Fuel Injection Pressure Regulator - Delphi, Standard Motor Products, AC Delco - TheAutoPartsShop - TheAutoPartsShop

As oldchevy said, check the wiring for the fuel sending unit...a frayed wire or bad ground can definitely cause the gauge fluctuation.

 

for the humming a good start point is to remove the belt and run the engine to see if the noise is still there or not if it goes away then spin each pulley by hand and see if you can hear or feel the bearings groaning/wobbling

 

If you hear it when truck is still get a rod or a theascope like the doctors got and find it