Fuel Pump Rattle???

[jww1955]

I've got an 88 4.0L and there's a rattle coming from the back. It makes noise whether I'm moving or not so I don't think it is related to the drivetrain. I checked out the retaining ring for the fuel pump on the tank and it seems to be tight. Is there any way the pump could be hitting the tank or just be loose? It seems to be getting louder so I'm a bit concerned. Has anyone experienced this before and knows how to fix it?

By the way, I replaced the stock fuel pump with a Bosch about 3 years ago and don't recall this noise happening until recently.

Thanks,
Joe