I found this post when I was googled a search for my problem and thought it was worth a shot.
I have a 2010 with 7,000 miles on it. It is under warranty and I have been to a couple of dealers and I get the same response. "Heard the noise, cannot diagnose, pinpoint or locate any faults. The noise occurs after 4,000 rpm advise consumer not to exceed 4,000 rpm's it is not recommended to exceed these rpm's and is not advised."
So I guess this means I should not attempt to pass anyone or let my automatic shift when it shifts. passing gear mostly.
I initially thought it was detonation, tried several grades of gas and different stations. no luck!
then I tried locating a damaged heat shield / weld could not locate any broken welds but clamped the heat shields anyway, No change!
then I thought loose element in catalytic converter. dropped it all is fine!
then I removed flex plate inspection cover, bolts tight and no cracks could be observed!
then I thought it was lifter bleed off and tried a different grade of oil 5w30 Amsoil. Although it did not fix this noise it definitely is quieter at idle and smoother running.
then after more searches came across the video with the same noise and then this post which makes the most sense as of now.
I have had the ECU flash as mentioned earlier on when they replaced my leaking transmission cooling lines. no fix but maybe thats when this noise started!
All I know is it is driving me completely insane every time I get on the freeway, go up a steep grade or pass someone! it happens when up to operating temp the worst does it slightly in park when revved. also I tried and put it in 2nd gear once to keep it from shifting and drove above 4,000 rpm's briefly and it does it and when I let off the gas it does it until the rpm's drop. which makes sense that it happens when I hit passing gear and goes away completely when it upshifts.
I need help