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Question: What can cause this noise?

I have a 1998 Dodge Ram 1500 Sport. I had a slow power steering leak that has sped up to where I have to replace the entire fluid every day. Now it has started to make this grinding/humming noise when i turn and even go straight. The noise goes away though when I push on the gas. It only makes the noise when rolling forward without any power from the pedal being applied. It sounds like its coming from the center right position on the truck. Also when i put it in reverse it feels like something is holding up the front wheels. A little history I recently had the u joints replaced and a full brake replacement done. Newer tires, and just had it in the shop to have a tune up done and they didnt report any problems after looking it over. Im puzzled and would take it into my mechanic but It is saturday. Any ideas?