Popping in the rear axle

Viking Jeeper

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I've got a popping noise coming from the rear axle in 2006 LJ Rubicon. This started yesterday as a subtle noise and now is quite noisy. The popping comes from the rear axle whenever the vehicle is moving and either the clutch is depressed or coasting to a stop out of gear. It does not happen when accelerating or maintaining a constant speed. I have not had the time to replace any fluids in this Jeep that I've only had two weeks or so. Any idea what the noise is?

Since I will be replacing the rear diff fluid now I have a question on that also. I've read many people here suggest that non-synthetic gear oil is preferred in the differentials but the FSM indicates Synthetic 75W-140 for the rear Rubicon axle. What gear oil is preferred for the rear Rubicon axle?
 
Mine wasn't consistent, but popped a few times in the front. Upon opening my diff I discovered it coming from my front spider gears in the Rubi locker.
 
The LSD might be breaking apart. Mine is doing that right now. Loud cracks and pops during turns. The diff will occasionally lock up during a turn. Mostly quiet in straight line driving. Changes between forward and reverse can be loud.

Pull the cover and you'll likely find metal chunks. There is no fix. I'm waiting for an ARB to arrive.
 
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The LSD might be breaking apart. Mine is doing that right now. Loud cracks and pops during turns. The diff will occasionally lock up during a turn. Mostly quiet in straight line driving. Changes between forward and reverse can be loud.

Pull the cover and you'll likely find metal chunks. There is no fix. I'm waiting for an ARB to arrive.
Mine seems to be quiet in turns, noisy in straight line. Only makes noise when the drivetrain is not driving the vehicle, only when clutch is depressed or coasting.
 
Mine seems to be quiet in turns, noisy in straight line. Only makes noise when the drivetrain is not driving the vehicle, only when clutch is depressed or coasting.

Get the wheels in the air and start turning and spinning.
 
Those symptoms are typical of driveshaft U-joint failing. Maybe remove the rear driveshaft and drive with only the front wheels and see if the noise persists.
The driveshaft does not have much play in it when I get under the Jeep and twist/pull/push, would a failing U-joint show a lot of play in that way? If its a U-joint I'm ok as I figure I need a new DC driveshaft after tuck.
Get the wheels in the air and start turning and spinning.
I did that recently when I was doing some other work. Did not notice any noise and opposite wheel turned opposite direction when I spun them.