Jack her up put her in nuetral and roll the rear tire if its a rea end problem I bet you will feel it. if not then I wouls take the plugs out and put it in fist and roll it over by hand (Still jacked up and rolling rear tire) then second adn so on. if the rear does not make the noise then it is in the tranny. Then I would ask how mechanically inclinded you are?
How many Miles and do you lubricate the drive shaft every 10,000 miles if your a dark sider or at every tire change if you use a MC tire and I mean the drive shaft splines not the one that go into the tire hub.
pictured below you have to take the final drive differential off
