Obligatory 'Strange Noise' Topic, Caliper's Locked Up? Options

[senick]

Well, I have a 95 AT200 w/AT. Lately (for the past month) I've been hearing a noise from underneath. It's on and off, and mostly there's no noise. But when it happens, it's at low speeds, and it sounds like metal on metal contact, like the brakes are rubbing (which is what it could be). My theory is that it might be the exhaust, as I've already had some ghetto welding done on it, but I think the cat's breaking from the inside out, and the metal shavings burning on the inside are what's making the noise, which would explain the intermittent nature of the noise and why I usually only hear it at low speed. Does that sound reasonable?
As far as symptoms, she's driving like a top, aside from some rough idling at times. Shifts are great, no misfiring, oil and trans fluid are fine, engine temp good. I just had the passenger side CV axle replaced, and I know the sound isn't coming from the driver's side.
I know this is a pretty poor explanation of the problem, but if it happens again I'll try to record it and then you guys can hear it. But meantime, do you think it could be the exhaust?

Edit: The noise seems to amplify when I hit a sharp incline, or roll through a low spot in a parking lot, so that the front of the car is higher than the back.

This post has been edited by senick: Oct 6, 2011 - 10:10 AM

[senick]

Well, it sounds like metal on metal, and has a harmonic frequency to it. What would the hub bearing sound like? It's not a screech or a creak, but there is some tapping to it. If I had to say, it's more like grinding.
So, I've yet to hear the noise if I'm in park and hit the accelerator, but I do hear it occasionally while idling (which makes me think it's exhaust). If I'm in park and turn the wheels there's no noise.