My 2006 H3 Hummer is having a vibrating nosie under the front passenger side of the vehcile between 1500 and 2000 rpms. The only visibly worn part was the passenger side front differential mounting bracket. I've replaced that and I still have the problem.
Front end vibration on 2006 Hummer H3
On passenger side, below exhaust manifold right where exhaust starts to run horizontal to ground is a heat shield on top of exhaust pipe. It has a metal strap around it . Mine broke, rusted . It's a 2008 H3 with only 6,500 miles, never been off road. Good thing it started rattling because looking for noise found front drive shaft boot on transfer case broke to pieces throwing grease all over. Will take in for warranty, hopefully better rubber boot. Not feeling good about durability of my tough hummer!