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Flowmaster American Thunder Classic Axle-Back Exhaust (13-14 GT)

57 Reviews
Our Price

$434.99

  • Item #18443
  • MPN #817588
  • Market Price $484.99
  • You Save 10% ($50.00)
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Product Videos Customer Photos
Features
  • Aggressive Flowmaster Super 44 Series Sound
  • Polished stainless steel 4" tips
  • Durable 409 Stainless Steel Construction
  • Includes two Flowmaster mufflers
  • Direct fit replacement upgrade
  • Made in the USA
  • Fits 2013-2014 GT Mustangs
Description
Classic Flowmaster Sound. Give your 2013-2014 GT that unmistakeable Flowmaster sound with a nice power boost with the American Thunder Axle-Back exhaust system. This system improves exhaust flow using Flowmaster's patented chambered muffler design for that throaty, aggressive exhaust tone your high powered Pony deserves.

Quality Construction. Constructed from durable 3" 409 stainless steel tubing for its resistance to corrosion, the Flowmaster axle back features two special 5" X 10" chambered Super 44 Series Flowmaster mufflers with 4" diameter polished stainless steel tips for muscle car looks and sound. As an added bonus the tip is embossed with the "Flowmaster" logo for true custom styling.

Direct Fit Upgrade. This Flowmaster American Thunder Classic Axle-Back Exhaust includes all the hangers and clamps needed to bolt  up in the stock factory location without any modifications required, making it a direct fit replacement upgrade.

Application. This Flowmaster American Thunder Axle-Back exhaust system is designed to fit the 2013-2014 GT models equipped with the Coyote 5.0L 4V V8 engine.

Mustang Fitment: 2013 2014 Details

What's in the Box
  • (2) Mufflers
  • (2) 3/8" Hanger Keepers
Installation Info
Tech Specs
Axleback Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : Polished Stainless Steel
Piping Size: 3" Tip Size: 4"
Muffler Type: Chambered Fitment: 2013-2014 GT 
Fitment
  • Boss 302 - 13
  • GT - 13, 14

Most Helpful Reviews View All

Overall Rating 4.9/5 Write a Review
5/5
These Flowmaster axle-backs are amazing!!

I purchased my first Mustang (a 2013 GT) in late November. I absolutely love the car, but there were a few mod’s I definitely wanted to make right away. The first mod on my list was a new exhaust. The

Read More
Helpful (6) (0)

5/5
Simply Amazing

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

Read More
Helpful (4) (0)

Videos

Hi I’m Justin with AmericanMuscle.com, and I’m taking a closer look at the American Thunder classic axle back exhaust fitting the 2013 Mustang GT and GT500. The classic from Flowmaster gets its name from View Full Transcript

Customer Photos (12) View All

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Q & A (1 Questions, 3 Answers) Ask a Question

Do you need a tune after install?

Dave1360 Year: 2013 Model: GT

Question Resolved
Good Question (0) (0)
  • No Tune needed, Just enjoy the sound!!!

    Helpful (0) (0)

    Beerz Year: 2013 Model: GT

    Top 500 Contributor

Show 2 more answers

Reviews (57) Write a Review

  • 5 Stars .89 89%
  • 4 Stars .07 7%
  • 3 Stars .04 4%
  • 2 Stars 0 0%
  • 1 Stars 0 0%
4.9

out of 5 stars

55 Customers Recommend this Product

Installation Time:Afternoon

Installation Cost:0-$100

  • Loudness / Volume: 4.701755 4.7/5
  • Exhaust Note: 4.842105 4.8/5
  • Fit & Finish: 4.842105 4.8/5
  • Bang For Your Buck: 4.68421 4.7/5
Filter By Sort By
  • 5/5

    These Flowmaster axle-backs are amazing!!

    January 23, 2013

    I purchased my first Mustang (a 2013 GT) in late November. I absolutely love the car, but there were a few mod’s I definitely wanted to make right away. The first mod on my list was a new exhaust. The factory exhaust didn’t give the powerful muscle car sound I wanted and expected. This is my first Mustang (and first Muscle car), so I did a lot of reading and watched a lot of youtube videos to find out what might be best for the sound I’m looking for. I decided to go with the Flowmaster American Thunder; which I am so happy I choose! They sound AMAZING! From inside the car, I can definitely hear a deep, rumble in the lower RPM’s and when I get on it, my baby roars! Not an annoying moan, but a low, rumble like you’d expect to hear from a race car. Heads are definitely turning now! :) The installation was fairly easy – It took just over an hour. Getting the factory mufflers off was a little hard to do on my own, but I was able to handle it. There were no surprises, but having an extra set of hands would be helpful and backing the rear wheels up onto something to lift it 6 inches or so is recommended for easier access and room to work. I highly recommend purchasing the American Thunder – The price is good and they sounds great. You won’t regret the purchase. Next on the list is a cold air intake, then a tune! AmericanMusclecom is my new favorite website!!

    SELENE

    Year: 2013 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 1 Beaverton, OR, USA

    Helpful (6) (0)

  • 5/5

    Simply Amazing

    April 08, 2013

    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!

    Red14

    Year: 2014 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 1

    Helpful (4) (0)

  • 5/5

    This is what a Mustang 5.0 GT should sound like !!

    June 11, 2013

    I took my time trying to compare many of the videos , stock exhaust to the Flow Master products, I didn't want the wrong kind of attention so I knew i didn't want the straight pipes. These American Thunder series sound sweet, as soon as it fired up a big smile came over me. but I also noticed a few other nice things happening. The engine obviously is breathing much better, I can feel a welcomed crisper response on the throttle, the fuel economy actually went up 1 tick " or " point one or .1 was getting 19.3 MPG and as soon as i got a test run on the new pipes it went to 19.4 MPG AVG . I am 100% satisfied with these pipes. LOVE EM !!!

    VolumetricEfficiency

    Year: 2014 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2 Alabama

    Helpful (2) (0)

  • 5/5

    Flowmaster American Thunder Classic Axle-Back

    November 10, 2012

    The installation of the mufflers was easy overall, but I did need an extra set of hands to help me push the pipes back to get the factory mufflers off. Once this was done, putting the new mufflers on went without a hitch. I already have a set of these on my 2012 5.0, so putting these on my wife's 2013 5.0 went much smoother. This exhaust added a much meaner sound to our Ponies! I would recommend these to anyone who is looking for an upgrade to their exhaust.

    Alfred

    Year: 2013 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 3 Houston, TX, USA

    Helpful (3) (1)

  • 5/5

    Sound great, super easy install.

    December 24, 2014

    I shopped around for quite a while to find the right axle backs, listening to clips, reading reviews, etc. I went with these because they had a good sound and no loud raspy sound under throttle. They are perfect in my opinion, the fit is excellent and took me about 30-40 mins to install using a set of ramps and a ratchet. I'd consider myself above average on mechanical ability, but even a novice should be able to handle it in less than 2 hours for sure. There is no drone that I can find, I went through the gears and cruising 50-75mph in 6th gear. If you want an aggressive sound without being irritatingly loud, these are perfect. The sound clips on this site represent it pretty well, but they are a bit louder in person, which is what I hoped for. I couldn't be happier with these, and the folks at American Muscle got them here faster than I expected, ordered on a Saturday and at my door, from Pennsylvania to Louisiana, Tuesday morning. Packaged well, tips protected, definitely recommend the mufflers and American Muscle. I will be buying anything I need or want for my car from here.

    TimFromBama

    Year: 2014 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 5 Louisiana, USA

    Helpful (1) (0)

  • 5/5

    Now that's what I call a premium sound system!

    May 13, 2014

    This is the first real mod that I have performed on my 2014 GT. I was looking for a louder and more distinct sound from my ride and I am thrilled with the results. The online guide to installation was pretty good, and I did it in a little over two hours. The most difficult job was removing the old axle back as space to pull it off is pretty tight. The difference in the exhaust note is quite evident, a much more "throaty" quality at start up, and a very nice rumble when cruising at low speed. When I punch it, I am rewarded with that sound only a Mustang can make, and the way it resonates when you downshift is very satisfying. Heads definitely turn when I drive by. I was a little concerned about the drone some reviewers have experienced. Although I do notice what you could describe as a drone at about 1600 rpms, it is not what I consider irritating or even significant. Overall I am very satisfied with the Flowmaster American Thunder Classic.

    barnacle989

    Year: 2014 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 5+ Columbus, OH, USA

    Helpful (1) (0)

  • 5/5

    Great Sound!!!

    June 25, 2013

    I just received these in the mail Yesterday, I Took them to Midas and Steve Installed them for me for 47.00. Very glad I took them there, as I helped him install these I realized it would have really sucked to do this in my Garage. On a lift it's a little bit of a pain to get the stock ones off, on my back it would of been a real bad day. Once they are on though, the smile stretches from ear to ear, sounds so Deep and Throaty! This should be the stock sound, Love everything about it. Wife hates them so I know I did good! The Drone is acceptable, I just love this sound!

    Beerz

    Year: 2013 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2

    Helpful (3) (2)

  • 5/5

    Perfect Choice

    June 18, 2013

    Like so many others, I spent numerous times reading reviews, and watching u-tube clips. I had it down to the Roush and the Flowmaster American Thunders. I chose the Thunders because they provided some back pressure so I did not need to worry about any chance of burning my valves over time. Also, some had complained about the muffler body on the Roush coming apart which concerned me. Centering the Thunders was easy and the sound is perfect...a nice rumble at freeway speed and an awesome muscular note when accelerating. I am very happy with this product and can say without a doubt that you will be happy as well. Definitely worth the money. Thanks American Muscle.

    StrongPony

    Year: 2014 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 5 El Paso, TX

    Helpful (1) (0)

  • 3/5

    2013 gt flowmaster AT classic axle back

    February 16, 2013

    After SEARCHING for months for a good set of axle backs I finally settled with these American thunder classics. Most kits were for 11-13 gt's witch concerned me because the rears of the 13's are slightly different and I was afraid of fittment issues. These AT classics for the 2013 gt fit PERFECTLY on my car and took about 1.5-2 hrs to install. I HIGHLY recommend removing the hangers and using a lift if possible! These are supposed to be made of stainless steel? So I don't know why flowmaster would paint everything except for the 4in tips? The sound is OK and there is a GOOD amount if drone. They are loud but not as loud as everyone made them out to be. If I had to do it over again I would have payed the extra 30$ for the roush axle backs. For 439$ I was expecting something a bit better. In both quality AND sound..

    ddinn25

    Year: 2013 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 4 Lebanon OH

    Helpful (2) (5)

  • 5/5

    Awesome

    February 15, 2013

    Easy install, great price, sounds great , nice n loud

    Jojodanca

    Year: 2013 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 3

    Helpful (1) (4)

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