My 2004 Chev Suburban Z71 4WD started making grinding like sounds that I couldn't really locate (my hearing isn't as good as it was when I was younger - I'm 54 now). Anyway, last year I'd replaced my front right wheel bearing assembly and the sound was similar so I replaced the left front (that didn't help, but at least I've got that done since with 190,000 miles, it was destined to go, right?). Ok, so I surmised it might be coming from the rear so I replaced both carrier bearings (next to the differential), both wheel beaings, and last week the rear drive shaft universal joints (I didn't have the driveshaft rebalanced due to budgetary reasons though I wanted to). Next, I got word from a friend that his suburban made a similar noise and it turned out just to the fluid in the transfer case. Today, I drained my own transfer case and I did notice some metalic feel to the fluid though it could have been normal wear and tear. Still, the noise remains. I'm contemplating changing the universal joints on the front axle, but I'm uncertain how difficult that is. Does anyone have a suggestion?