I have a '97 Cavalier, 2.2, 4-Speed automatic that has an unusual rattling sound upon hard acceleration. The car has only 9000 miles on a new engine and the engine is quiet at idle and when revved up. The noise gets louder as you accelerate harder. Normal acceleration you really can't here it. No transmission issues, regarding hard shifts, slippage or gear shift vibration. I searched this site for this issue, but did not find something specific. Any ideas would be appreciated.
My GF's vert was making a noise similar. It ended up being the catalytic converter shield. But I think it was rattling at idle as well.
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'96 Cav Vert (GF's)
'04 GSXR-750