definate;y check your u joints tho buddy b4 you buy a rearend.jack it up and see if you have anything unusual going on withem.lift up and down ,side 2 side .and you could take five minutes and just pull the shaft and seee how they are .if u have acces to a lift have someone put it in gear wile ure under EASILY put in gear.drive then reverse etc see if the shaft or joints are moving at all .joint are famous for clicking also .its the easiest to hoop for.good luck.
mods:2004 sierra ext sb,20s ,big brake kit w,hawk pads,air bagged,2006 6.0 lq4 swap,vortec supercharged10psi, air to water intercooled w/ dual electric fans on it ,snow meth injection kit,60lbers, e-fans ,big radiator swap ,cam 218 /222 548/550 comp .hardened prs .1.85 comp roller rockers ,guideplates ,crane double springs,trans 4l65e built .pacesetter l/ts true duals w/x pipe and magnaflows,14 bolt rearend swap ,3.73s,aroemotive fuel pump system w/elec.fuel controller and bypass regulator a/n fittings, taylor 10.5s interceptor gauge,aem w/b a/f ,autometer boost/vac NELSON 93 OCTANE TUNED .