Re: "Clunking/knocking" Rear Diff.?
Changing the fluid will unfortunately do nothing at this point if it is makng that much noise. Mine did that too, which was a bad carrier bearing, which made noise only when on the throttle or going uphill. I would not wait any longer to get it repaired; when a bearing freezes up it will ruin a lot more things inside there and could be several thousand for a rebuild at that point.
2006 GC Overland QD II
5.7 Hemi, Modern Muscle 85 mm CNC ported TB, Apexi super voltage stabilizer, Billet Tech. Catch Can, Koni FSD shocks/struts, SRT8 sway bars, Cooper AT3's, Amsoil fluids, Diablosport Intune CMR tuned by Hemifever tuning.