Did my 7.25 take a crap?

pulling the diff cover is going to tell the tale, i think you also need to see if it moves under its own power also...even pushing it in neutral w/o the car running should produce this mystery noise if its the carrier...or better yet put it in neutral, and then jack up the rear, spin the tires by hand (both forward with you and a buddy to simulate rolling down the road) and the noise should be easy to source...if its a u joint you can grab the driveshaft in park and it'll be excessively sloppy....anyways lucky for you ppl give those 7.25's away ( i know i have) so finding a new center section, or complete rear for free/cheap will be easy.