Well, it's not the fluid nor filter-both are fresh. I also dissassembled and inspected the loader and backhoe valve bodies. I also dissassembled the quick-connects to make sure they had no obstructions.
Perhaps I'm not adequately describing the symptom: It's not really a loud, high-pitched whine, but more of a slightly audible noise when the machine is in neutral hydraulic position. It's a noise that sounds like the pump is under load. I'm hypothesizing that the problem could be with a stuck relief valve. I think this because the noise goes away while an attachment (either loader or backhoe) is moving. Do relief valves commonly get stuck?
THe other thing is that the noise is not that bad, but I've never noticed it before and it just doesn't sound like I think a smooth running machine ought to. THat said, I don't want to fix something that isn't broken.
Thanks,
Brady