Help!!
 

I have a 2008 Hummer H3 with only 80k miles. When I'm driving city speed limits I dont hear it but when I'm driving on highway 70mph I hear this noise and I let go of accelerator ir goes away and when i push it starts up again only when I'm going 70mph and above I hear the noise. Can someone shed some light on this!

i wonder what it sounds like?

It's not a grinding noise I'm guessing it can be drive shaft u joint.

OK, so I had a similar noise for almost 25,000 miles, kind of like a grinding sound but more of a nuisance sound then a sound you could relate to a possible component failure. Searched everywhere and narrowed it down to speed related, not engine rpm related, so that basically pointed to the drivetrain and all it's associated parts and not the engine and transmission. I took apart the emergency brake, checked U joints, drive shafts, rear; still nothing.
Bottom line is the 3rd time I removed my tires I notice that the inside of my chrome rims were deteriorating to the point that the chrome plating was peeling up and then rubbing on the brake calipers as the wheels went around. Some pieces were 3" and peeled up about 1/2-3/4".
I found and installed a set of new rims and problem solved.