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Flowmaster American Thunder Axle-Back Exhaust (15-17 GT)

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Market Price $703.99 You Save 12% ($82.04)
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$621.95

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  • Item 384452

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    Features, Videos & Details

    • Aggressive Flowmaster Super 44 Series Sound
    • Durable 409 Stainless Steel Construction
    • 2.5" Mandrel-Bent Tubing
    • 4" Polished 304 Stainless Steel Tips
    • Includes (2) Flowmaster Super 44 Series Mufflers
    • Compatible with Fastback and Convertible
    • Fits All 2015-2017 GT Mustangs

    Review & Installation Video

    Hey, everybody. Justin with AmericanMuscle.com here, taking a quick look at the American Thunder Axle-Back from Flowmaster fitting your 2015 Ford Mustang GT. Flowmaster is, without a doubt, one of the most recognizable names in the Mustang world, and it has been the hot rodders' choice for many decades. Now, we've used several of their products in some of our past builds, including the recent BAMA Terminator. If you guys haven't seen these builds yet, what are you waiting for? Be sure to check out some of our project car builds in addition to the best Mustang specific content on the web by checking out our YouTube Channel, American Muscle videos. So the American Thunder from Flowmaster is one of those tried and true systems that sounds killer on just about every generation Mustang, including the new 2015 Coyote powered Ford Mustang GT. Now, that iconic sound comes courtesy of the Super 44 Series mufflers here which will give your S550 just a little bit more bark, but won't wake the neighbors in the process. The entire system has been constructed from durable 409 grade stainless steel and features this durable high-temp black coating here, which should help reduce any corrosion over the years. Piping is all 2-1/2 inch mandrel bent, and we're looking at 4-inch slash cut tips embossed with that iconic Flowmaster logo. Now, guys, if I haven't answered every single one of your questions about the American Thunder here and you'd like to see more detailed information along with some detailed install tips, then be sure to check out the product page at AmericanMuscle.com if you haven't already done so. As you may or may not have heard by now, installing an Axle-Back onto your 2015 Mustang will require some cutting, as is the case here with the Flowmaster American Thunder. But don't worry. As long as you take your time, follow the detailed instructions, you should have no problems knocking it out in about an hour from start to finish. Either way, guys, if you do have any more questions about the exhaust or about the actual install, feel free to reach out to one of our Mustang experts any time using the 1-800 number. They're always standing by, ready to help a fellow Mustang owner in need. Now, it's time to hear how the Flowmaster American Thunder Axle-Back sounds compared to the factory exhaust.

    Classic Flowmaster Sound. Add the unmistakable Flowmaster sound to your S550 GT with an American Thunder Series Axle-Back Exhaust System from AmericanMuscle. This axle-back system improves exhaust flow using Flowmaster's Super 44 Series mufflers for that classic aggressive muscle car exhaust note your high powered Pony deserves.

    Stainless Steel Construction. Constructed from durable 2.5" 16 gauge 409 stainless steel tubing for it's corrosion resistant properties, the Flowmaster American Thunder Axle-Back features Super 44 Series mufflers with massive 4.0" diameter polished 304 stainless steel tips for impressive muscle car looks and sound. As an added bonus, the tips are embossed with the "Flowmaster" logo for true custom styling.

    Cut & Clamp Installation. The installation of this Axle-Back Exhaust requires cutting and removing the factory muffler assemblies and clamping the new muffler assemblies in place. Clamps and instructions are provided.

    Application. This Flowmaster American Thunder Series Axle-Back Exhaust System is designed to fit the 2015-2017 GT Mustangs, including fastback and convertible models.

    Fitment: 2015 2016 2017 Details

    MPN# 817749

    CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

    What's in the Box
    • (2) Muffler assemblies
    Installation Info
    Tech Specs
    Axle-Back Exhaust Specifications
    Piping Material: 409 Stainless Steel Tip Material : Polished 304 Stainless Steel
    Piping Size: 2.5" Tip Size: 4"
    Muffler Type: Chambered Fitment: 2015-2017 GT
    Will it fit my Mustang?

      Customer Photos (13) Submit Your Photo

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        Questions & Answers (9)

        5 Top Rated Questions

        I already did a flowmaster resonator delete x pipe still running the stock mufflers. Will this system bolt up to that without further cutting?

        • The installation of Flowmaster American Thunder Axle-Back Exhaust would require cutting and removing the factory mufflers and clamping the new mufflers in place.

        Helpful (3)

        Does the brace for convertible cars go back on after?

        • Yes, the brace can be reinstalled after installing this exhaust on your convertible Mustang.

        Helpful (0)

        what would be best resonator delete option for American thunder axle back?

        what's the weight on this set up?

        • The Flowmaster American Thunder Axle-Back Exhaust weighs around 49 lbs.

        Helpful (0)

        will my car still pass emissions testing in NJ with this system? thanks

        • Yes, you car will still pass emissions testing in New Jersey with the Flowmaster American Thunder Axle-Back Exhaust, the system is legal in all 50 states.

        Helpful (0)
        Post Your Question
        4 More Questions
        Will this axleback be a direct bolt-on to the boss 302 style mid pipe? 1 answer
        Will this exhaust fit a GT Convertible? 1 answer
        My current 2015 Mustang GT already has a Catback Flowmaster Exhaust system on it . I just bought this car, even though I am not crazy about how loud it is. The previous owner of the car had the resonator removed AND had a cold air filter system added on it. I think that the current FM mufflers on it are not sufficient enough to handle the additional air flow and power. Can these replace the ones that are there now and will calm the beast some? Thanks for your time. 1 answer
        Will this be able to be run in-line with my Ford Racing X-Pipe? Or will it require a shop custom fab this on? I'm afraid that the use of four clamps from the X-Pipe to the mufflers will make the exhaust unstable. 1 answer

          Customer Reviews (47) Write a Review

          Overall Rating 4.6

          out of 5 stars

          Installation Time:Full Day

          Installation Cost:$100-$250

          • Loudness / Volume 4.046512 4.0
          • Exhaust Note 4.674418 4.7
          • Fit & Finish 4.581395 4.6
          • Bang For Your Buck 4.604651 4.6



          • 5/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            April 18, 2019

            Excellent Tone

            Beats the stock 2017 GT exhaust by a long shot. Loudest during cold start and the first 30 seconds and then it brings out its nice thundery bass in idle. The deep undertones surrounding your car before you get inside sure makes you feel good. Underneath a gas station canopy, people will admire the non-obnoxious beefy sound. When the stop lights turn green, you can give your engine the gas and the American Thunders will shake anyone dumb enough to get too close behind you. It does give you some road sound presence which creates room between cars. I live in an apartment so I park far away from first floor windows and face the exhaust away also. I use the Snow/Wet mode to better control noise when leaving the parking lot at 4:30AM. No complaints from anyone. I’d consider getting a Sound Tube Delete and an H-pipe installed at a later time. Sometimes I wonder how the Axle-Back Borla Touring compares to the Axle-Back Flowmaster American Thunders. With either choice, I think the H-pipe or stock resonator is enough with this exhaust system.

            Moosetang

            Year: 2017 Submodel: GT

            Helpful (0)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            January 12, 2019

            Flowmaster Custom axle backs

            I had the outlaws and an X-pipe with stock exhaust manifolds and cats it was ok, but then I added full length BBK ceramic coated headers and the off road cat delete kit and then the sound was TOO LOUD for my liking also too raspy. So I purchased the flowmaster super 44s and an H-pipe from AM and had a shop install them. WOW! WOW! WOW! EXACTLY WHAT I WAS LOOKING FOR! Now it’s nive and deep and throaty without ANY raspy sounds. If your a muscle car enthusiast and love the sound of classic muscle cars with big cams and engines then this is the set-up to get.

            JonathanI

            Year: 2017 Submodel: GT

            Helpful (2)

          • 5/5

            Installation Time: Less than 1 Hour

            November 18, 2018

            Easy to please

            Awesome design and engineering makes this an easy install. Sounds awesome

            BobV

            Year: 2017 Submodel: GT

            Helpful (3)

          • 5/5

            Installation Time: Afternoon

            November 16, 2018

            Awesome

            Little loud on cold starts but calms down. Paired with heart throb h pipe

            JoshR

            Year: 2017 Submodel: GT

            Helpful (4)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            October 23, 2018

            Nice!

            The Flowmaster Thunder was just what I was looking for ... a little more growl than the stock axle backs. These have a deep throaty sound, but without much of a drone. I opted for the shop install because what I saw was probably biting off more than I could handle. Since I have a convertible not only the stock ones had to be cut (just like on a coupe) but also the rear body brace had to be taken off.

            RogerS

            Year: 2015 Submodel: GT

            Helpful (5)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            September 01, 2018

            Just right

            After going through 3 exhaust systems on my S197 I was determined to get it right the first time around. It took me months looking on different sites, listening to audio clips and reading reviews to find the exhaust that's just right. I didn't want drone or something that was so loud you couldn't listen to the radio and talk to someone at the same time. For me it's the perfect balance and it has the right amount of popping in sport mode. Very pleased

            WlknTal

            Year: 2017 Submodel: GT

            Helpful (7)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: 0-$100

            June 15, 2018

            A different perspective

            First off the delivery and condition of this item are both OUTSTANDING. Arrived a day early. Next, considering the sound, these have been called "mild". That's ONLY relative to the crazy loud, siren call, headache inducing, watch the world burn systems out there. This is deep without the awkward shudder sound of stock. Paired with the SR X pipe and it's CLEAN. More than enough. Listen to the YouTube videos on speakers with bass; not through your phone. It's a good choice.

            GabrielB

            Year: 2017 Submodel: GT

            Helpful (10)

          • 4/5

            March 12, 2018

            Great sound

            Over all good product. Sounds great with the sound not too loud inside the car. I also installed an x pipe with this. The sound with factory resonator is too quiet. I Had to bend one of the hangers on the passenger side to get the tip to line up properly with the cut out in the bumper. Over all it was a good buy and i am happy with it.

            Dan

            Year: 2015 Submodel: GT

            Helpful (9)

          • 5/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            December 12, 2017

            Classic Muscle Car Sound

            Installed these axle backs on my 2016 GT convertible. Deeper tone that is moderately louder than stock. A more aggressive tone overall but not obnoxious. No complaints. Will be installing an H-pipe soon to go with them. I recommend these for anyone looking for a classic deep throated muscle car sound for their S550.

            ToddO

            Year: 2016 Submodel: GT

            Helpful (9)

          • 3/5

            Installation Time: Afternoon

            November 29, 2017

            Sounds meh.

            Flowmaster makes a great product. Good quality- but in those particular axle back, it just wasn’t the sound I️ was looking for. They’ve got a great growl when you get into the higher RPM’s, but I️ wanted a sound that had a presence at an idle. I️ paired this axle back with a Corsa double helix X and cut the cats. Still too quiet for me, but a great product and does a have a good sound. Just not the growl I️ was going for.

            TalonT

            Year: 2017 Submodel: GT

            Helpful (7)

          • 5/5

            October 22, 2017

            Happy

            Overall I really like the song of these. Wish they were a tiny louder but great for my daily.

            Robert

            Year: 2016 Submodel: GT

            Helpful (6)

          • 3/5

            Installation Time: Afternoon

            October 03, 2017

            Sound great but has a drone from 1500-2000 RPM

            These sound great. But they have a pretty loud drone from 1500-2000 RPM. I also have the Flowmaster X pipe installed. So you may have different results with the factory resonator still installed. I haven't decided yet, but I may be removing them for another option. Too bad I welded them in. The clamps that come with them don't hold very well. They allow the mufflers to twist. And with all of the hangers on the same side, they will.

            TJK

            Year: 2015 Submodel: GT

            Helpful (7)

          • 5/5

            Installation Time: Less than 1 Hour

            October 03, 2017

            Love them

            I love them especially combined with the x pipe and the rest of the system. It does drone in 6th when pulling.

            Jlewis

            Year: 2016 Submodel: GT

            Helpful (6)

          • 4/5

            Installation Time: Afternoon

            September 16, 2017

            Stock GT "Wife's"

            Classic sound, loud enough for my wife without to much interior noise. If I ever want them louder I can just put an X on and wake it up. Kinda adjustable. They will not disappoint.

            Ross

            Year: 2016 Submodel: GT

            Helpful (6)

          • 5/5

            Installation Time: Afternoon

            September 13, 2017

            Flowmaster is the only way to go

            Had mustangs for years. Flowmaster has been on every one of them. If you're struggling to decide, let this review help you. Super 44's give the mustang its real muscle car sound. Sounds clips don't do justice, it catches everyone's ear while driving. The sound is not obnoxious, it's clean and mean. Like a stang should sound. Combo this specific pack with and h or x pipe, an h or x style resignator delete and you won't be sorry! Install was easy, sound and flow are true. IMO the 44 series wake the car up. As you add more modes, it unleashes more!!

            RalphC

            Year: 2017 Submodel: GT

            Helpful (12)

          • 4/5

            Installation Time: Shop Install

            Installation Cost: $100-$250

            September 08, 2017

            sound

            Great quality good product, That being said, the black paint on the mufflers were pretty scratched up when I opened the box, also Its actually not quite the sound I was looking for, I think with this double overhead cam engine (like a Japanese speed bike) I may try a straight through muffler next time but Ill have to save my lunch money for awhile before I try something different, so many to choose from and the sound clips just dont do it. I like how it sounds at speed but not at idle.

            Matt

            Year: 2015 Submodel: GT

            Helpful (7)

          • 5/5

            Installation Time: Less than 1 Hour

            September 02, 2017

            How the S550 should have came from factory!

            I removed the factory resonator as well using the Flowmaster xpipe and this is just the best sound for your Mustang! Love it. I'm getting huge reviews from others at car shows. Thanks American Muscle!

            DavidL

            Year: 2015 Submodel: GT

            Helpful (6)

          • 5/5

            July 28, 2017

            American Thunder

            Love the sound! Sounds more like a muscle car without being obnoxiously loud. Originally installed a different axle back system and found it to be too loud. My 2015 Mustang GT now has the H-pipe resonator delete with American Thunder and sounds great. Fit and finish are excellent. Installed using my Quick Lift in about two hours.

            Kab

            Year: 2015 Submodel: GT

            Helpful (7)

          • 3/5

            Installation Time: Shop Install

            June 19, 2017

            Drone

            Too much drone. But way better than the Roush. The drone is pretty bad with the "H-Pipe". The Roush with the "H-Pipe" sounded horrible. It sounds nice outside the car...low rumble sound compared to the raspy, tinny sound of the Roush.

            Jimbo2738

            Year: 2016 Submodel: GT

            Helpful (10)

          • 4/5

            Installation Time: Less than 1 Hour

            June 09, 2017

            Good sound

            These sound great. I did not want anything too loud. However there was a bit of drone in the car but I believe that removing the resinator on the car caused this. There is an oddo from the coating buring off for a few weeks.

            RyanR

            Year: 2016 Submodel: GT

            Helpful (10)

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