MIne makes noise if I am not in the gas or going up hill keeping a load on it.. If at cruising speeds, it'll make noise..
The blue stuff they put on the splines is gone on mine, so I'm assuming its the clearance causing the issue.
Before I lifted mine, it made noise also, but I greased it up and that went away. The minute I drove it after the lift kit (4.5") it made noise - even if I greased it.. Talked to JEREEL (drive shaft shop out here locally) and they say they hear that all the time..