Unidentified Noise (which wasn't there before...)

[Nomake Wan]

Okay guys, I'm back. And now I've got a bit of a problem.

I did a full flush for engine and transmission... it solved lots of problems, including my MPG and my tranny's hard shifts. But now I'm getting something really weird.

If I push the pedal to rev and the revs are between 2k and 3k, there's this grindy/whiny sound from the engine bay. You can barely hear it from 2k to 2.5k... but from 2.5k to 3k it gets really obvious. Then after 3k it just disappears.

I've already confirmed that it's not a slipping belt, according to my dad. He says that it's not loud enough, not the right sound. He also has no idea what this sound is.

I don't know whether it's something slipping or my tranny grinding... I hope it's the former, because tranny grinding on a 67k mile Legacy is just sad.

If any of you have heard this, I'd love to know what it is. And if you have no idea what I'm talking about, I guess I could take a video of me driving along and hope that the mic catches the sound.

Also, as far as I can tell, it doesn't appear to happen if I'm in neutral and rev. Only while in Drive.

Thanks in advance, guys.

[tris91ricer]

hmmm.... does it occur in all gears, or just D?

[Nomake Wan]

Umm... pretty sure it occurs in "3" and Drive. I haven't tested 1 and 2. Hang on, I'll go do that right now.

Yep, it appears to do it under WOT in all gears. The worst, however, is if it's in D and the speed's around 35 MPH... revs'll be around 1.8k with cruising throttle... then if you go to WOT it shifts and the revs hit 2.6k and there's this awful noise...

But the more I hear it, the more I am convinced that either:

A.) The catalytic converter heat shield that has been rattling since forever is now at the point where it has a resonant frequency that is attuned to the engine at a certain RPM and causes that noise

-or-

B.) The transmission is no longer shifting properly, and is instead grinding shifts.

Again, I would love for it to be the former. However, I can't seem to find the battery for my camera, so I can't make a movie clip of the sound right now.

[LaureltheQueen]

my brother's gl did that with the heat shield. sounded nasty

[Nomake Wan]

Well, the noise isn't the "pebbles in a tin can" rattle that the heat shield does at low RPMs (like when backing out of the driveway). Like I said... it's a whining noise that covers the sound of the engine revving, and only exists under acceleration from 2000 RPMs to 3000 RPMs. Not a belt-slipping noise, but maybe a grind or something.

I found the camera battery, so I'll try to get a video clip.