Differential noise would appreciate any advice

[Manns53]

 

Bought this truck about 6 months ago didn't have this noise, started noticing it the last 30 days or so. Just changed the U joints and axle bearings, had seals leaking a little and had just started hearing a Ujoint pop a little so no loss there but they didn't take care of this noise. It's a surging rubbing sound almost that increases with the speed of the vehicle until about 25 or 30 mph. Probably still a faint wine higher speeds but it blends in with road noise and you don't notice it as much. But it's pretty bad from 0-30 enough to hear it outside the truck. Didn't notice any excessive wear on the ring and pinion everything looked ok to me when had axles out. No play in the driveshaft or pinion bearing. I took the ebrake shoes off for awhile to rule those out, no change. But in trying to isolate the noise I got it up on jack stands and put it in gear, crawled under it, and the diff would make a clunk about every 5-10 seconds like the carrier was locking up for a second. Pretty loud pop. Never does this while driving. Didn't know if this was normal with no load on it? But while in the air it def sounds like the noise is coming from the differential. Why I figured the axle bearings would solve this but no luck.

Pinion gear or main bearings?

Doesnt look like diff has ever been changed or messed with but could be wrong.