I have moved about 100 m3 of dirt last year: in time of foor and mouth disease, we were not allowed to move hogs. We had to store them all, in the machine barn and the narrow stripe of land inbetween the barns. I dug out 60 cm of mud and shit, replaced it by 50 cm of clean earth dug up in the forest, all with a 2 meter wide, 1.25 m3 earth scoop.
I checked the final drive oil, clean as new. But, when you are working hard, letting the engine die down in low range reverse, use the diff lock or your satelite carrier shaft in the differential will wear a little hard.... I will check my diff when i have time....
Those rear ends are unbreakable in work... You have to use mean tricks to snap them, as long as you use them properly (no smashing into a big pile of sand in high gear), it doesn't matter how heavy the load. Just use the diff lock.