[hr]I posted this this before but missed the tech section. I did my u joints today and they ain't it. Hello, I am new to forum and am looking foward to learning alot. I previously owned Silverados and own now a 99 Sierra SLE 4x4 Ext. Cab 5.3l with 130,000. 4 in Fabtech lift. anyways, along with the usual "burp" or "thump" when taking off or stopping I have a fairly loud growling noise that seems to be around the rear end. Changed the fluid and noticed only minor shavings. U joints look beat so those will be next. Maybe a pinion bearing? The noise increases with accel and decreases with slowing down but cuts off if I coast in neutral. I am a decent backyard mechanic but have yet to tackle a rear end. Other than the noise it drives fine. Could this be coming down the line from the transfer case?? Any advice would be greatly appreciated. My pre 99 C/Ks never had this happen.