Ok i admit i only searched for a short time, but the results were extremely difficult to pin down to something similar to what im hearing so here it is.

I'm getting this oscillating metallic type of whine around 2400rpm and under acceleration coming from the rear. FYI, its a 2008 coupe with a 6MT. I took a good look underneath and didnt see any issues with the u-joint or anything else. I also tried to tighten up the drive shaft bolts but it still persists and they didnt really feel loose. It sounds almost like a bad bearing, but it only does it around 2400rpm and only when im on the gas. It makes the noise in any gear, but always around the same rpm range and it doesnt seem to be speed dependent. Its possible the noise is always there but drowned out by the exhaust or engine noise at lower or higher rpms. theres also vibration i can feel through the shifter but only when i hold it.

I know this isnt easy to diagnose like this, but any help is appreciated. Im still thinking a u-joint is the likely culprit even though they werent rusty and didnt feel loose or look damaged.

thanks

 

If its RPM dependent its harmonic noise from the engine, clutch, transmission or any/all combination of those. Mine is noisy below 2300/2400rpm under high load and even at idle. Switching to a lightweight twin disc made mine even louder. Seems to be pretty common with these cars.

Do you have an aftermarket clutch/flywheel?

 

The clutch is still original, but the noise is def coming from the rear of the car and doesnt sound like a harmonic type of thing. I know the car is just naturally noisy, but this sounds like something is up. I can be at the right rpm range and coasting/slowing and not hear the noise. Its only when im on the gas at that range that i hear a noise, but it very well could be there the whole time and its not discernible over the other noises.

Maybe its the rear diff when under load. At 82k miles the fluid is probably at the end of its life and i doubt its been changed by the previous owner. I already have plans to swap out the tranny and rear diff oil this spring.

 

Rear diff noise would be vehicle speed dependent. Engine RPM harmonics could enhance a vehicle speed related sound, or change a noise or whatever. Have you drained out your rear diff oil? Probably a good start.. See if any chunks come out....

 

When this is happen, depress the clutch and modulate the engine speed. Does the whine change pitch?

It does to some extent in my car, but only when ambient temp is over 65-70F and car is fully warmed up. Changing the trans fluid to a synthetic made a big difference in the volume. Not very noticeable at higher speeds because of greater wind noise.