Within the last two weeks (after my last time wheeling) I have noticed after about 15mph this "noise". It sounds like a rattle/bearing noise. seems to be coming from the transmission or transfercase area. Its not very loud, but noticable with the radio off, and fan on a slow speed. The sound does stay at a constant tone. It does not fluctuate with the speed of the jeep. Which is what has me so confused. I would think if it was a drivetrain issue it would get louder or quieter with speed. What do you guys think I should check, or what could be causing this. I just want to make sure its nothing serious. Thanks. Oh, the jeep is 98 with manual transmission.