pop quiz hotshots....j/k whenever i shift from, or rev to and let off the gas pedal at 4k i hear this noise come from under the hood, i cannot pinpoint what it is..... it's not metal on metal it almost sounds like when you rip a piece of paper fast or something, it's a very accurate it sound, it happens whenever the tach is at or right around 4k. any ideas, it's hard to explain the type of sound it makes, but what happens at 4k, does a valve or something open??? any ideas what it could be??? it's a 98 ls by the way

thanks guys

 

jack the car up and have someone look at where they hear it the most and someone hold the gas at that particular rpm. I just took my heat sheild off for the same thing. It would rattle at between 3800 and 4000. No more problem. It was the one right underneath the shifter.

 

Is it somewhat of a whirring sound? My GS-R used to do the same thing at 3-3.5k. I know it sounds like it's coming from under the hood, but it's really coming from under you...the heat shield I think.