Apprentice Mistakes
2008 Ford F250 2wd 5.4l. Shop apprentice (with the assistance of another tech) just replaced rear park brake shoes. Installed loaded backing plates. I finished an electrical repair on it, then test drove. Right rear caliper hung up. Checked everything, replaced the caliper brake hose. Test drove again. Right rear wheel locked up solid. Got it freed up and limped back to the shop. Tore everything back apart, couldn't find anything obvious, reassemble and drive in the lot. Binding/scraping/clicking from right rear. Test it apart again, systematically eliminated the park brake shoes, caliper, brake pad. Finally pulled the axle shaft, and...chunks fell out. Seems the kid forgot to top off the diff fluid when he was done. Oops. Fortunately, it's a fleet, and we caught it before we put the truck back in service.