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Discussion Starter #1 (Edited)
Hey all.
I did a fair amount of searching on this topic before posting, but couldn’t find anything exactly like what I’m looking for, so here goes.

The car is a 2002 325Ci, manual transmission. It’s in great working order, but I’ve noticed that between 3.5-4K RPM in lower gears, there’s a loud “oscillating” vibration coming from the dash. It is not a “rattle.” It does cause a rattling noise I guess, but its the vibration causing it.

This occurs in neutral if you rev the engine up to the range I mentioned, and also happens in 1st, 2nd and 3rd gears. It’s not noticeable in 4th or 5th. The vibration is also not speed dependent, it seems specifically RPM dependent. The vibration goes away entirely once you surpass 4K RPM, until you shift up and dip back down below 3.5K. Rinse and repeat.

I recently replaced the guibo when I did the shifter bushings, so that’s not it. (And yes, the vibration was a thing before I did that). When I was doing that I also replaced the CSB, so it’s not that either.

The vibration is not perceivable from the steering wheel, seat, or shifter. It’s isolated to the dash. If you place your hand on top of the dash near the center, you can feel the vibration.

I took it to my mechanic and they said it was the flywheel needed resurfacing. But I’ve had flywheels go out before, and I really don’t think that’s the issue. I’m really hoping someone here has a recommendation, because I’m worried the problem will get worse over time. The previous owner said this has been an issue since he bought the car about a year ago (I bought it back in March this year), and he said he wasn’t too worried about it. His opinion is that it’s something loose in the dash, maybe some insulation/rubber/a loose screw. Not sure what to think.

If it helps, I’ll take a video on my commute tomorrow morning and throw it up on YouTube as soon as I can.

Any help appreciated. Thank you!
 

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2004 330Ci 85k miles
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I would have a helper do some revving while I check in the engine bay and underneath car.
Vibration is coming from engine/clutch revs, since it happens in neutral when car is stationary.
Flywheel or clutch sound like culprits.
Engine and trans mounts all good?
 

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Definitely not the flywheel needing resurfacing! The clutch is engaged and there should be minimal slippage. Can you feel the vibration in the gear shifter? Has any work been performed in the dash? Pop the head unit out and put your hand on the dash support bar. It runs from the left side of the dash to the right side. See if you can feel the vibration in it.
 

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Discussion Starter #4
I would have a helper do some revving while I check in the engine bay and underneath car.
Vibration is coming from engine/clutch revs, since it happens in neutral when car is stationary.
Flywheel or clutch sound like culprits.
Engine and trans mounts all good?
I’ll see if I can get my girlfriend to help me out with that a bit later today. Transmission mounts are brand new- did those along with the guibo. Motor mounts seem fine, I couldn’t see any wear when I inspected them, and the engine is stationary.

Definitely not the flywheel needing resurfacing! The clutch is engaged and there should be minimal slippage. Can you feel the vibration in the gear shifter? Has any work been performed in the dash? Pop the head unit out and put your hand on the dash support bar. It runs from the left side of the dash to the right side. See if you can feel the vibration in it.
The shifter does vibrate but I’m fairly sure that’s because I installed Poly and Aluminum bushings. Also since I didn’t mention earlier, the vibration is not perceivable in the clutch either. The car has had multiple owners, so I’m not sure if the dash has been worked on. I have not. I do know there’s an aftermarket head unit installed for the radio, could be something behind there. I’ll pop it out later and see if I can find the support bar you’re talking about.

I took some video of the sound this morning. I’m at the gym now but I’ll upload it to YouTube when I get home and post the link here.
 

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Discussion Starter #5
Here’s a link to the video I just uploaded:

Oh, and I should add- the temp is cold in this video but the vibration occurs regardless of the temperature.
 
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