New Driveline Noise problem

[HomelandPatriot]

Ive got a 2013GT Premium with brembos and track pack. Car has 15k miles on it, only a weekend driver and not my DD. Last night while heading into town, I noticed a sound though im not 100% sure where its coming from. It sounds like what can be described as a "yawn" as in the beginning of a big yawn you make when your tired.

I have found that it only happens on decel, and it only happens at almost exactly 40mph. If I'm in gear and coast and I pass 40mph while slowing down it does it. So far it doesn't do it when accelerating and it only does it at almost exactly 40mph. I can actually time it perfect by watching the speedometer and waiting to coast past 40mph.

I haven't noticed it while braking past 40mph, but its possible that its just a quicker sound while breaking because the sound is longer and shorter based on how much time I spend right around 40mph while decelerating.

I have headers, cat back exhaust, eibach pro lowering springs, a steeda PHB, steeda CAI and a ford racing short shifter along with a custom dyno tune.

I haven't noticed any performance loss or any abnormal driving, but the sound it obvious and brand new since yesterday.

Thanks

 

[HomelandPatriot]

Thought I'd add too that so far it doesn't seem to happen in neutral. Only right around 40mph, in gear and decelerating.

thanks

 

[INEEDA_TERMI]

Rear end whining on decel? Tranny? Is it gear specific?

 

[HomelandPatriot]

I haven't tried all gears but it is there in both 4th and 5th gear. I don't do much 6th gear driving and I haven't run 3rd up that far since this started. It seems more speed related than rpm related.

 

[Zandura99]

I would put my money on an exhaust whistle. I have cat deletes and x pipe, and I have a couple whistles that are annoying, but are not an exhaust leak just an issue with the sound from inside the pipes themselves. Easier to hear on decal because the motor noise isn't in the way...