Okay, I started getting a sound in the front-ish end of the TJ last week. NO wheeling for a while, but it just started making this noise. It sounds kind of like gears are not quite in sync.
In 2hi, 4hi, and 4lo, it makes the noise. it is not tied to engine speed, but rotational speed of the tires. I put the Jeep on jackstands in back and in 2hi, with only the rear wheels turning, no noise.
So I'm pretty sure it is the front.
I replaced diff fluid in front as I checked to see if I had blown the front end apart. they look great actually. So I got thinking either t-case or something else. I did an adjustment on the t-case lever thinking perhaps the gears weren't quite in sync. Noise still there, but it shifts between the 4x4 modes better.
So I'm beginning to wonder if it is the front ujoint. The yoke coming to the D30 looks like it is covered in oil/grease, but I see NO signs of pinion seal leak.
I even checked the t-case fluid level. It was fine.
I'm not sure if the is the 'angry sparrows' noise people complain about or what. I guess my next step is to put all 4 wheels in the air and get close while watching it (hard to isolate sound while driving).