Hey there! I'm new to this posting thread stuff! So, bear with me! I have a 2007 Cobalt. Love it! I've had it since 2006. Lately I've had a knocking noise under my car. I had a friend look at it. He thinks it is the control arm bushing. Can anyone out there tell me, how expensive of a job that is? Or would that be covered under the warranty? I looked, and I'm not sure! Thank you!