So I've got an 03 Auto, 225k miles. The old girl suddenly makes a chirping noise while shifting to reverse back to drive occasionally, as well as during driving through gears. I've replicated the noise when the car was parked and was being shaken, but also haven't been able to recreate it while doing the same. A much more knowledgeable friend of mine suggested it could be a gear box issue considering it makes the noise while driving. I've seen several posts about the tensioner being an issue in this model but I don't think it's what im experiencing, but im not ruling it out either. I'm quite sure it's not a belt as it's not a constant noise or a whirring noise.
Any thoughts here? I do have a bad cat in the old gal that's starting to get real loud so I shift into neutral while stopped quite often, which would make me lean toward a gearbox or some sort of other transmission issue.