Help with weird noise after installation of tbe exhaust

[scx89]

Hi everyone,

I'll apologize in advance if I'm posting this in the wrong section.

About a week ago, I installed q300 catted tbe on 11'wrx.. ever since then i've been pretty paranoid about everything being okay. (my friend told me his 11'sti's motor blew with only stg 2 flash + dp)

Now, when I'm in 2nd gear, decelerating without any brakes (just engine breaking)... at about 1600 rpms, I get a very different vibrational noise. While it's decelerating, i feel the car flutter very slightly (i think this is normal for all cars?) and I hear some sort of scratching/grinding noise from the front of the car. It's not a constant noise, it goes along with the flutter.

When the clutch is in and at the same rpms, there is no noise.

With that information, I can only guess it is something to do with the differentials/transmission?

I don't know if this noise was here before going putting on stage 2 mods.

Other things that might be a variable:
I lifted the car with a floor jack, using the differential on the front and back as a jacking point. Then set the car on jack stands.
I found the heatshield with 2 of the bolts broken off. I removed the heatshield and drove around, the noise is still present so it wasn't from the heatshield vibrations.
I installed the DP myself... (first time..)

thank you guys for your time! I'm deciding whether or not I should just go to the dealership and ask them what's going on... I just don't want to go to the dealership and have them flag me for mods b/c of warranty service.

 

[Grinder34]

I think its just your diff making normal noises.

Do you have any subie-driving friends around? You can sit in their car and see if you hear it there too, but it SOUNDS like its just some normal gearbox whine.

 

[scx89]

what do you mean rattling off?
it only makes the noise at 2nd gear and at the specific 1500-1900 rpms.. when its off throttle mostly.
i took a couple vids but you can barely hear it..
it flutters and the sound goes with the fluttering

i can't imagine it's a rattle because i should be hearing that rattle at other times..

i think i tmight be differentials normal noises but I want to be sure
Im not sure if it's air or grind/whine, but i do know that my data logs for a/f are all good.. and no exhaust leaks..

 

[HolyCrapItsFast]

I know what Rek is getting at and it was my thought as well... I'm thinking the DP is contacting with something and the noise is transfering through the body. Areas to check would likely be the center bearing of the drive shaft or farther down stream somewhere. Maybe run your hand along the DP and see if it comes close to anything.

 

[scx89]

how much is close? it's like 2-3 inches away from the front crossmember, maybe 1 1/2''. Ill get under sometime and check if there's any shiny rubbed areas..
Also going to do an exhaust leak test today with some bubble water.