Rear axle bearing I noticed a leak on the passenger side

Additional information: Limited slip calls for 75-140 synthetic which I used (but without friction modifier). I drove the truck with some chattering in the limited-slip differential before adding four ounces of friction modifier. Could this have caused the the bearing to get hot and/or the bearing cages to disintegrate?

Thanks for everyone's help. Still do not know for sure (likely low lubrication) what caused the bearings to come apart. I had used a China made $20/each bearings from Napa (did not know there were premium bearings).

Had used Valvoline 75-140 synthetic gear oil. Added friction modifier about 100 miles later when there was some chattering which eliminated the chattering. Valvoline did not include friction modifier.

Before installing new parts - I had to clean out a bunch of metal flecks which came from the disintegrated bearing cages and outer bearing race. So use a round toilet cleaning brush with an extension attached to it to scrub the axle housing while blowing in aerosolized diesel using a air-compressor attached that has a port to siphon in a liquid, in my case diesel. It took about 30 minutes of scrubbing on each side before no more metal flecks were coming out. Then clean the differential gears and housing and used a magnet to collect anything in the bottom of the housing.

What I did this time - I used a Napa premium bearing, $70/each, has USA made stamped into the side of the bearing. The bearing has 13 bearings and no cage. I also bought bearings from the Ford dealership just to compare them. Ford's bearing were made by the same company as Napa's premium bearing, but they looked different. Ford's bearing had a cage and fewer actual bearing (I think there were 11). Asked Napa for the supplier tech line and learned that the Ford bearing was an older OEM part and Napa bearing was the newer OEM part. Just seems to me that 13 bearing without a cage (Napa) is better then 11 with a cage (Ford) since both were USA made by the same company.

This time I used Mobile 1 75-140 synthetic gear oil which had friction modifier included. Called for 5.5 pints. Put in 6 pints and it is still about a 1/4 below the differential fill hole. Will keep a close eye on this since low lubrication is what several people suggesting was the problem.

Pre-oiled the bearings and even added a touch of bearing grease and greased the axle surface as well as the bearing seal.

All seem to have gone back together well. Again, thanks for all your help. I really appreciate it.