• Flowmaster American Thunder
  • Flowmaster American Thunder
  • Purchase the Flowmaster American Thunder Axle-Back Exhaust System for your 2015 GT Mustang from Steeda Autosports today!
  • You will not need anything else, this Flowmaster American Thunder Cat-Back Exhaust (05-10 GT, GT500) will bolt right up to your setup!

Flowmaster 817508 Cat-back System 409S - Dual Rear Exit - American Thunder - Aggressive Sound


We stopped by LaBree Motor-sports in Southern California where Brent LeBree and his son, Greg, were installing a Flowmaster American Thunder muffler on an '06 Mustang coupe.

I pulled off the stock mufflers (to the tune of 46 pounds for the pair) and slipped the Flowmaster American Thunders under the 2014 GT that I just picked up. The first thing that was noticed, was that the Flowmasters fit under the car so much better than stock. They don't hang below the rear valance and draw attention to themselves like the stock setup. Also, the full 4" tips fill out the exhaust cut-outs so much more appropriately. Then, I fired the car up. American Muscle does an outstanding job with their videos, but even they don't do justice to the throaty rumble coming from the back of the car. Night and day over stock. Great investment!


1970-1974 Chevy Camaro Flowmaster American Thunder Exhaust Kit #17149

There's no sound as uniquely American as that of a rumbling exhaust system. And there's no better way to get that awe-inspiring sound than by bolting on a Flowmaster American Thunder Exhaust System. With its mandrel-bent, free-flowing design and high-quality materials, the Flowmaster American Thunder is ready to sing - and bring the power.