I've looked through alot of post for this but I can't find if it's as been posted. I can hear a cherping nose coming from the engine area riding down the interstate. I don't hear this nose driving around town or anywhere alse but the interstate. I drive about 70-75. I've eliminated one of my theory's, it's not the a/c. All I can think of is maybe a pump. I thought maybe someone else as had this problem and could help me out.

Don't know how new your truck is, but I had a similar noise on my truck. On the first road trip a couple of weeks after I got it, driving down interstate, started getting popping/chirping noises. Only happened at certain times at certain speeds...annoying as crap.

Pulled over and started looking under truck. Noticed that there was paper/tape with GM part numbers on just about every cable under the truck....and all had frayed edges where the wind was popping them like bullwhips. Pulled all the paper off, noise gone.

Hope thats your issue.

I don't think thats it. I've had the truck since Oct. 04 and it started making the noise this summer.