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I have a 2015 base LT1 with 90,000 miles and for the past 10,000 miles or so, I have heard a sound from the engine that sounded like a bucket of bolts rattling when I shut the car down after a drive. That was the only time I noticed it. I took it to my dealership 6 months ago when it started and they didn’t have a resolution. Since my extended warranty is about to expire, I had the car serviced again to check the valves and that mysterious sound. Thankfully there is a new mechanic who came from another dealership and had experience with this issue.
When I learned of culprit, I of course went to the Forum and read about other owners having this issue, but interestingly, most have heard it while driving or idling. So for those you have that mysterious sound, here’s your issue and resolution.