As stated by the other posters, the sound that you describe is usually made by a manual gearbox that’s going bad. I’ve experienced a similar sound with two transmissions. One was a d series s20 trans in my 93 civic, and a 92 integra with Y1 that made the same noise. Both would even make the noise while in neutral. Also, these transmissions were prone to grinds and pop outs as well. A way for you to test to see if it’s the same problem I had is to listen, and see if the sound cuts out or changes while you are engaging and holding the clutch in, and if it comes back or sounds any different when you let off the clutch. If the sound doesn’t change at all by use of your clutch, I would say that you could eliminate the trans as possibility. But aside from the transmission, I have no clue what it could be. I never heard of alternators or any belt driven accessories making the noise you described. Could you attach a file or link of you recording the sound?

the noise from your transmission, as opposed to the rest of your drive train would be noticeably different. Anything related to your axles, wheel hubs, wheels, brakes, or whatever would have a speed dependant sound signature and would not be very distinct, due to the simple nature of these parts. On the otherhand, a transmission has many tiny and big parts all crammed inside the bell housing. When it makes a noise, it’s likely to make several different types depending on what’s going bad, and the noises will be distinct, somewhat unique.

You Tube

Hmm. Interesteing. It sounds a lot like gearbox chatter but You should have shifted gears or something so we could hear how the sound changes. I think you’re onto something as far as it being vibration related. But the fact that it goes away when the clutch is on still makes me feel that it’s gearbox related. I’m thinking the input shaft of the transmission. Someone correct me if I’m wrong, but doesn’t the input shaft spin inline with the engine no matter if the clutch is engaged or not?

You know, I once discovered acorns inside the air intake filter box of a friends ek sedan that I was doing work on, they made a rattling sound when driving that was caused by vibration. The damn sound was driving me nuts. Pun intended. Lol, but really, I was like “what the hell is that noise?” For days on end.

Okay now I’m really stumped. The only thing I can think of that makes rpm dependant noise is tires. And Tirea don’t sound like that. I’m no auto guru though, and diagnosing sounds is probably the weakest of my skills. Good luck!

And yes, squirrels. I don’t think they were living in it, just using it for winter food storage. There were seriously like 50 acorns in there right beneath the air filter... The car had been sitting for like 3 years before my friend owned it.

I’d be willing to bet exhaust. Especially since you have mentioned it rotted out