Just like a pipe organ inside a church,
the length of the tailpipe from muffler end to tailpipe end
determines the rpm where the 'drone' shows up.

I have found that 65 inch lengths give drones around 1900 rpm.
Lengths shorter give drones at higher rpms like yours at 2300, so I suspect your tailpipe length is already shorter than 60 inches or so.

You can move the drone up to even higher rpms by putting in the 'resonators' which are like mini mufflers. You can also move the drone up higher by going to short side exit tailpipes.

technical details if you are good at math:

http://www.gmi.edu/~drussell/GMI-Acoustics/Filters.html

 

I went to my dealer this morning so that I can let them know that this thing is not as quiet as their parts department made it out to be. I know it's not glass packs loud but the drone is starting to get worse and I'm getting a headache driving my truck. I took one of the service techs on a ride so he could hear it first hand, and he did. Upon our return, the head service guy (probably the manager) said I'm the first to come back and complain about the drone/resonance at 2000RPM or (it now seems to be between 1900-2300) but since his tech heard it, he can't refute it. He is convinced that performing TSB 11-002-05 will help mitigate it quite a bit and that he's going to get personally involved with this problem to see the drone is minimized/eliminated. TSB 11-002-05 is supposed to eliminate a drone/vibration at idle with the stock exhaust but I've read that Durango's had the same fix done to fix drone at 1900RPM. It adds a a sound dampener on the Y-pipe. I just don't know if that's going to fix it. I'm about two steps aways from calling tomorrow and demanding my stock exhaust (they apparantly still had it in the shop as of today) be put back on and that I be refunded the money for the exhaust as the parts department I think misinformed me. It's bothering me that bad. I've been in people's cars with aftermarket exhausts on other V8 type vehicles that don't drone like this. My buddy's Mercury Marauder, which has the same V8 as the '04 Mustang GT and a tuned 3" dual exhaust, does not drone like this at all. It's got that nice throaty sound one expects from a performance exhaust on a V8 without the annoying drone/resonance. F-ME!!!!!!!

 

Your exhaust was in the shop and you didn't throw it in the back of your truck, that is the first thing I'd have done had I saw it sitting there.

Regardless, it is good to know that the dealership seems to be standing behind thier products. Hope things work out for you.

 

Yeah, stupid move on my part. I'm just so frustrated by this I'm not thinking straight I guess!

 

No biggie, just call them first thing tomorrow and state that you want it back and that you'll stop by to pick it up on your way home. You did pay for it and it is yours.

 

The mercury Marauder does not have the same engine as any year mustang GT. It's closer to a lincoln Mark VIII, Mustang cobra (pre-supercharger), Mustang Mach 1 and Lincoln Aviator.

This adds nothing to the conversation of course... but still.

 

I thought the Lincoln Aviator and new Explorer has a revised 3V head on the old 4.6L modular as opposed to 2V heads on the Mustang GT and 4V heads on the Cobra/Mach 1.

 

Too busy at work today to call the dealership, I will be first thing tomorrow. I'm at the point where I'm ready to give up the ghost and have them put my stock exhaust back on and hope I don't have to get into a battle to get my money back on the Borla system. This is no joke, I'm getting a headache everytime I drive it. It's not so much the dB level of the exhaust, it's whatever resonant frequency this exhaust system is hitting in my cabin it's triggering the start of a migraine headache. I should've just appreciated how nice the stock exhaust sounded, letting my CAI do the rumbling when I go wide open throttle. Boy I sure hope it's not going to be a huge battle in getting my money back.

 

The new explorer (and mustang and F-150 and Mark LT) has a mod motor with 3V heads. All the cars I mentioned have 4V heads. My point, with reference to this post is that SOHC and DOHC engines sound completly different, and that in turn pushrods are even differenter-er

 

Gotcha. We were on the same page, just didn't realize it.