Tuesday morning my '08 HUMMER H3 started making a very odd noise when I left the driveway. It is deep in the lower part of the dashboard. My first instinct was a fan or belt as it sounds like a rapid whining sound ( I know that is vague but the noise is so odd that is the best way I can explain it). It started at 20 mph, disappeared, reappeared at 30 mph, then road noise takes over and I can't tell if its there over 40 mph or not. I called my dealer this morning and they are very backed up and said they had no appointments left this week for service. When I told him what the problem was he said "that doesn't sound good. Stop by so I can hear it and if its something I think will leave you stranded I'll give you a loaner." So after work and driving 30 miles I pick up the service tech and we go for a ride and wouldn't you know the damn sound is gone. Once the vehicle is warmed up it disappears. We started to hear it very lightly twice, and he said just from what he could hear it sounds like the catalytic converter. He told me it wouldn't leave me stranded and made an appointment for me to come back Monday afternoon. I don't know why but I'm worried it may be the transmission; with it being directly related to my acceleration. Would a tranny problem make a belt-type noise deep in the dashboard? FYI I have no check engine light, rpms are not erratic, no "feeling" of anything wrong... just noise. Anyone have an opinion on this issue? I'm afraid to drive it until I can get it in Monday. Thanks, Trish

 

Almost impossible to accurately asses what problem you might have based upon a "it makes this sound" description since we cannot hear it.... but, have you looked at the heat shield over the exhaust manifold?

The often crack and/or then make contact with something and make some funky noises. You can always inspect and pull it away from the manifold?

Good luck.

 

My guess would be the heat shield, mine does the same thing. Anytime it gets around 2200 rpm it makes a rattle sound and it sounds like it's coming from either the tranny or front axle, but it's the heat shield rattling around.