Hello. Recently a truck I put out at work came back with a broken axle shaft . The axle broke right at the outside of the hub and allowed the bearings and jam nuts to fall off. The inside of the hub got so hot it melted the bearing and one nut to the shaft. We had to cut everything off to get the hub off. The shaft also wore into the differential spindle housing. This is a double drive axle body job peterbilt.
Prior to being sent out brake shoes, drums, cam shafts, bearings , seals, and spiders were replaced. The hubs were prefilled with oil, shafts were checked, and the differential oil was changed. Apparently the driver got stuck and flipped on his diff lock. Question is, with all things considered, how could a 3" or so shaft shear off? The diff was also checked and showed no major signs of damage. The mating axle shaft however did show abnormal wear.