when you push the clutch does the noise go away or change volume.
I had that type noise once years ago, it must have been the throw out bearing, but like many things on the old jeep over the years, it made less and less noise and now its been years since I have heard the noise.
clutch works fine.
(guess it tired of waiting for me to fixed the problem, so it fixed itself)
when you hear the noise, take the belts off and see if you still hear the noise, could be a water pump, alternator bearing, power steering bearing.
check all fluid levels front/rear differentials, transfer case, trans, motor oil levels