I know there are a lot of posts about weird sounds, but I think I have one that has not been listed...Whenever i am 3k rpm's and I let off the gas to cruise, usually in 4th or 5th gear, I get a weird sound that reminds me of microphone feedback...It's not that loud but sometimes it gets loud, especially around 60-70mph. I only have about 500 miles on her, and she is 1 week old. Is this a normal sound to hear during the break in period, and if so has anyone else heard this sound?

 

it's probably the engine revving down.

 

I know what the engine rev sounds like and the intake sound, and its not one of those.

 

so it's a high-pitched squeal?

 

Its not a squeal, its a steady high pitched hum, feedback from a microphone is the only way I can think of to describe it...

 

could be road noise..I dunno

 

While I dont own a tC, i believe you are hearing the same noise that my manual trans. Mitsubishi makes, and to a very much lesser extent, my xB will as well under the right conditions. I'm not positive this is what it is, but there aren't many options as to what else it could be. That said, ...i'm pretty sure what you're hearing is the noise of the transmission gears connecting along the backside of the gears.

Disclaimer : I'm not a trained mechanic...so check this with someone who really knows what they're doing.

When you're under power (and this is very simplified), the gear on the input shaft of the transmission has a load on the leading edge of each gear tooth...and the gear on the other shaft (i forget it's technical term) gets the load from the leading edge of the input shaft on the trailing edge.

This reverses when you let off the gas and assuming you are in the same gear you were before under power, you're somewhere in the transition between coasting and engine braking. Now the trailing edge of the input shaft has a load on it, and the leading edge of the other shaft has a load....the way the gears are cut i believe makes this noise.

Now, please someone correct me if i'm wrong, but i'm relatively sure this is the explanation for the noise you hear.

 

it either is the engine or raod noise. my engine didnt make any abnormal sounds doring break in

 

I noticed the exact same sound from my '06 manual during the first 1k miles. Right at 3k rpm, when i let off the pedal, it would make a high pitched whistling noise ... I just attributed it to resonance because it happened at such an exact rpm. In any event, I don't notice it anymore and no damage has occured to my car at all (several thousand miles later).

Note that this is NOT the same high pitched whistling noise that comes from acceleration (which is due to air rushing into the throttle body).

I wouldn't worry about it unless you notice obvious engine/tranny problems in the near future.
Ravi

 

It is coming from the intake and the VVT-i changing stages. I have a injen cold air intake and the sound is a little bit stronger, people have come up to me asking if I had a turbo.

 

After installing the engine damper, I hear this sound too. I would assume it's the engine winding....but who knows ?

 

Thanks for all the input!

 

yea I think it may be the tranny

 

um, just to point out something O.O

you aren't suppose to use cruise in the break-in period

 

I hear the same high pitched hum. I notice it it when I keep 40 in 4th gear, especialy when on cruise control. It's denfinitly comming from the transmission. I think of getting a synthetic transmission fluid which will decrease the friction.

 

No you guys dont get it, thats what it is. Open your hood and have some one give your car gas while in neutral and listen to the the intake, you will hear it even more. I know what im talking about.

 

I know what the intake and turbo sounds like. This is not an intake! You can only hear it when you keep constant speed. When you push the gas and start accelerating it stops. But I'm sure thats the way the transmission is, SCION is not a luxury car so you shouldn't expect perfect noise isolation.

 

OK you dont under stand, I know the sound you are talkin about. When you are driving on the freeway crusing between 60mph or so, it makes a whistle. There is nothing that is part of the transmission that would make any sound even remotely like that. Im telling you, but your car in neutral, open the hood, rev, and you WILL here it. I know what im talking about, no more stupid posts like these ones, it just gives stupid people a chance to try and show that they know something.

 

Exactly. 65mph, 5th gear, let off the gas and it whistles. Can be repeated in any gear with the engine RPMs at roughly 3000.

 

My point exactly. THANK YOU for not being retarded haha.