strange "rotational" noise like a bad u-joint

[BubbaRand]

seems to come from front diff - new CV axle, hub is fine - new front drive shaft - BAD noise in part-time 4x4, had to exit that fast - bad noise continued for a few blocks, then stopped but original "u-joint" sound continues - that this mean front diff is shot? Please help.

 

[ikuo78]

Check the transfer oil and differential oil.
Shake all the shafts held by bearings and check for looseness.

 

[u2slow]

I drove the jeep on axle stands to isolate my drivetrain noise. (Thought it was the t-case).

After trying both 2wd and 4wd with no sound change, I pulled the rear driveshaft. Then the sound went away. It was the rear axle pinion bearings.