Causes of diff bearing wear

Last week, I took my 2015 Ram 2500 into my mechanic to have a rear limited slip diff installed. To his surprise, most of the diff bearings, and especially the pinion bearing showed signs of severe wear despite only having 23K on the odometer. I purchased this truck used with 19K, and was told the truck had been gently used. What would have caused so much wear/damage to the bearings, especially the pinion bearing?

Sounds like someone loves to spin the tires to me.

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Or exceeded its capacity.

Too much backlash on initial buildup or pinion nut not torqued to specs or have come loose .
Could also be improperly hardened pinion during manufacturing or the most likely cause is lots of excessive towing .

I would like to see pictures. An improperly torqued pinion won't wear out carrier caps. To have ALL bearings showing abnormal wear suggests a lubrication problem to me. Assuming this is legit, I'd take photos, button the diff back up, and take it to a warranty dealer.

Hopefully, I can pick the truck up tomorrow and will take pictures of the pinion especially. I don't know the names of the bearings, but there were two round donut like bearings about axle size in diameter that were slightly discolored a light blue as well with some mild scoring on them as well. Again, I will take pics. I contacted the dealership and asked them about the problem, and they want to see the bearings as well. Since they did not do the work, I am out the cost of the bearing kit, which was about $700. I never would have known there was an issue unless we had torn it apart. I found out that before me, the truck had spent the first 6 months of its life as a "fleet" vehicle, so I suspect it had been abused. Fortunately, and despite having the 6.7 Cummins, I don't tow anything. I do carry a Lance 825 camper, which was made for a half ton pickup. And even with it on board, still get 21 mpg!!! I plan on taking it up the AlCan highway in the spring.

One last note, the bearings which are on the outside of each axle by the wheels were in perfect condition.

sI old the truck after the dealership stated it had been used to tow something way too heavy which is saying a lot with a Cummins. I am now the proud owner of a 3500 SLT

I don'the know what two "doughnut" looking bearing's could be in a 3/4T Cummins rear axle, except maybe the carrier bearings. "Turned blue-colored" sounds like lack of lubrication and/or overloading to me. Scoring sounds like contamination and/or overloading to me. Yeah, I agree somebody towed something really heavy and for long distance/ heavy grade.