Yesterday I had my differential rebuilt by the dealer under warranty. Is there a break-in period for the new bearings? The gears weren't replaced, so I don't have to worry about that (actually they looked brand new when I took a look inside last week before taking it in). Here is what the dealer said on the report card:

EAR AXLE/DRIVE LINE UNITS: 6.10 TECHS
CK FOR NOISE COMING REAR MORE SO UNDER LOAD
6.1 OVERHAULED REAR DIFF ASSY FOUND CARRIER BEARINGS BAD AND CONTAMINATION THROUGHOUT HOUSING DIAGNOSIS AND REPLACED PINION BEARINGS, RACES AND SEALS AND CRUSH SLEEVE REPLACED CARRIER BEARINGS AND RACES. REPLACED AXLE BEARINGS AND SEALS. ADDED FRICTION MODIFIER AND 75W140 SYNTHETIC REAR DIFF FLUID
CLEANED OFF EXCESS OIL TEST DROVE OK REPAIR DONE

I've been searching on the internet, only coming across truck part store pages saying 500 mile break-in period followed by a diff oil change.

 

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I would suggest you call the tech who did the work and ask what is recommended. I have not seen anything in the past on this, and would most likely go with the factory recommendation.