Strange grinding noise at 3000RPM

[Loki]

Alright this has been bugging me for awhile so I figure I'll ask the cool side of the formus. Whenever I let off the throttle (while in gear) and let the RPMs drop on their own there's always this semi-loud grinding noise coming from the engine. It seems to always be right at 3000RPM and only when the revs drop. I even hear it occasionally when I upshift.

Has anyone ever heard of something like this? I can try and record the sound if anyone would like. I haven't noticed anything really wrong with the car other than this noise.

[yijima]

hmm could be like my car. it's only going in 2nd and 3rd gear, when i get to around 3000rpms. but you said the noise is coming from your engine. so we may not have the same problems. but mine has to do with the transmission, to help narrow the possibilities down.

[LingeringSuicide]

timing chain guides?

[Loki]

It's not a rattle though. I had timing chain rattle on my first 240 and I know what that sounds like.

[94_240sx]

Do you think it's possible to come from clutch/flywheel or is it from under the hood?