After lots of searching - I don't see any threads with my exact symptoms!
 

Hey Everybody,

I have an 07 6MT GT with about 23k miles. Today when I was picking up a friend, he said "what was that?" and I had no clue what he was talking about. I turned off the radio, and did another "loop" around the parking lot, when I came to a stop, I heard it - it sounded a lot like a metal on metal sound, similar to when a bike chain comes loose on a bike (not like a screetching sound).

After some investigation, we determined that we cannot recreate this issue at will. It happened when I was turning, it happens when going into first gear, and when going into 2nd gear at very slow speeds. The sound ALSO occurs when I am decelerating on a decline.

Fast forward to this evening - I drove around with my wife, radio off, windows down, and we both heard it a few times. She thinks it's coming from passenger side (which I originally thought as well) but then while driving around, i stuck my head out the window and it sounded like it was coming from my side. I think it may realistically be coming from under the car. The best way for me to describe is is as if there is a chain that has come off of a sprocket, or maybe like a baseball card in the spokes of a bicycle. Another way to describe it would be as if there is some sort of metal dragging from the car. It seems to only last for a few seconds, in low RPM ranges. It is definitely NOT constant which makes it frustrating, I also have heard the sound when turning, and while going straight. I would try to get a video / audio file of the sound happening, but like I said it is not constant. The temperature here today was very hot, I'm not sure if that has anything to do with it.

I have some suspicions after reading many threads on rattles / sounds - I think it might be the sound of my cat going bad (for those who have had cats go bad - is the rattling constant?), or possibly something else in the exhaust system. I do NOT think it is the wheel bearing or lug nuts because the sound is not reproducible when the same variables are applied. I also do not think it's the differential because the sound goes away instead of getting louder when RPM's / speed is increased. That reminds me - there is no power loss / stuttering / or noticeable changes in the way the car behaves while this sound occurs. I think I sort of feel it in my clutch petal when the sound occurs during acceleration, it's very difficult to describe, it almost feels as if the clutch petal is tapping against my foot in sync with the "chain coming loose".

I know this is a lot of info and a lot to digest but I want to get as much to you guys as possible to help me figure this thing out! I also don't think it's an exhaust hanger because again, it's not consistent (I can drive the same route 4-5 times, accelerate and decelerate similarly, and sometimes it makes the sound, sometimes it doesn't).

What do you guys think??

Feel free to throw things out there, I'm very willing to answer questions / take pictures under the car / etc!

oh, also, it happened once as I was beginning to accelerate in reverse.

Do you have your AC on when this is happening? it could be the AC motor kicking in...

Is this it? Let us know...


http://www.finishlineperformance.com...2-04-1301b.pdf

^ Sounds like it...

yup +1

Nope, AC is off

I don't think that's it - I experience the issue going in a straight line as well - and the VIN is not in my range (that seems to only affect 2004's) - I'll still check it out, but it doesn't quite "fit" my symptoms.

also, one key piece of information i realize i missed - the sound definitely sounds like it is coming from the rear of the car - originally we thought it was the rear wheels. The sound is not coming from the engine compartment.

Something trapped in the rotors/pads?

Something wrapped around a spinning suspension component back there?

I don't think it's something trapped in the rotors / pads, because I would expect the noise to be more constant if that were the case.

I guess there could be something wrapped around some spinning suspension component - but I didn't notice anything when i peeked under the car (I will jack it up this weekend)

I did find this (active) thread - https://www.rx8club.com/series-i-trouble-shooting-95/whats-noise-217860/ - and the sound clip that the OP has there is nearly identical to what I have - one suggestion was pebbles caught in the heat shield...

I have an 08 with almost the same miles as you. My LSD started making a lot of noise at around 20K and it totaly cleared up when I changed the diff fluid. The sound was like the sound of disc breaks with no pad left when you make a tight turn at low speeds, especially in reverse. It is the LSD clutches binding on each other.

CV joints on the axle (if we have them)

good news everybody - I haven't been able to fix / determine what it is, but I am now able to re-create the sound at will. If I accelerate quickly, or accelerate up a hill, the FIRST instance of doing one of those two things will re-create, and then if I decelerate quickly, or decelerate down a hill, I hear it again (and won't hear it again until I accelerate on flat ground, or an incline)... Seems to me as if this is a sure sign that something is loose either in my exhaust, or as previously suggested, pebbles that got caught in my heat shield.

I'll update this weekend once I get under the car - but I'm thankful that it probably isn't anything serious

its definitely the heat shield, the question is now how to snap it back in place...im going to do something soon cause its a horrible sound that takes away from listening to the engine..