Jeepnfm

I can't figure out where I have this noise that just started today as well as drivetrain pop under load. I was out wheelin' today and everything was fine, then the "competition" started, sandy hill climb, I had to make a few runs and there was some serious front wheel hop a few times. Then leaving the area I started having a serious whine almost growl noise and pop in the drive train. 2wd there is no noise, 4hi and 4lo it is normal except under load and horrible sounding, almost like it's jumping gears somewhere. I just changed all fluids about a month ago. Any idea where to start on this? I have a feeling it's the Tcase but I'm hoping it's axle shafts or R&P cause I'm wanting to upgrade anyways, maybe the axle disconnect? 125,000 miles, 2.5 I4, 30f 35r, np231j, ax15