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

Market Price $531.07 You Save 12% ($61.10)

$469.97

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  • Item 18443
  • MPN# 817588

In Stock Ships same business day. Choose options to add to cart

Features, Video & Details

  • Aggressive Flowmaster Super 44 Series Sound
  • Durable 409 Stainless Steel Construction
  • 2.75" Mandel-Bent Tubing
  • 4" Polished Stainless Steel Tips
  • Super 44 Series Mufflers
  • Direct Fit Replacement Upgrade
  • Made in the USA
  • Fits 2013-2014 GT Mustangs

Review & Installation Video

Review & Install Video

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 (2) 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 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.

Fitment: 2013 2014 Details

What's in the Box
  • (2) Mufflers
  • (2) 3/8" Hanger Keepers
Installation Info
Tech Specs
Axle-Back 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 
Will it fit my Mustang?
  • Boss 302 - 13
  • GT - 13, 14

Most Helpful Reviews

5/5
Quick install

Minimal time with excellent return on investment. Love the sound, classic muscle exhaust note.

Helpful (1)

5/5
Verry Happy owner

It took me awhile to pick out which set I wanted for my car. I'am completely satsfied with my American Thunder 44 serious mufflers and I would recomend them to anyone that owns a newer mustang gt.

Helpful (1)

Overall Rating 4.7 out of 5 stars
Read All 72 Reviews

Customer Photos (12) Submit Your Photo

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6 Questions / 8 Answers

Ask a Question

I'm wondering if the American thunder is the 60 delta flow muffler or the 44 series? In the video for the force 2 Justin says that the American thunder is the 60 series. I want the 60 series not sure which one to purchase. Thank you

Robert

Answer This Question I need this answered (0) (0)

Is there a difference in axle backs from 2011-2012 to 2013-2014? I would like to run the Super 44 Series mufflers, listed here fitting 2013-2014 GT models. Will these fit on a 2012 GT?

Cleveland

  • I'm not sure if there's a difference but I have those on my 14 GT and they sound so good.... Super 44'series

    bill2014

    Good Answer (0) (1)

Answer This Question I need this answered (0) (0)

I currently have the Outlaw series on my 13 GT...... I do love the aggressive sound but it is a daily driver and the cabin noise and drone is a little too much for me, ( I bought the car with these already installed) Does this series tone it down or does someone have recommendations for a different axel back ?

GTIRISH

  • I have these on my car my buddy has the outlaws on his we both agree American Thunder sounds amazing. But to answer your question your going to have less cabin drown but not as much.....

    bill2014

    Good Answer (1) (0)

Answer This Question I need this answered (0) (0)

will these void factory warranty?

ImpactBlues

  • Not at all put them on and it will sound good

    bill2014

    Good Answer (0) (0)

Answer This Question I need this answered (0) (0)

Do you need a tune after install?

2013StangDC

  • No Tune needed, Just enjoy the sound!!!

    Beerz

    Good Answer (1) (0)

Show 2 more answers Question Resolved

I bought a pair of these a few months ago and I love their sound but the Drone is horrible from 1700rpm to 2200rpm. Is there anything that I can do to reduce the Drone?

KungFuCooter

  • To reduce the drone, additional mufflers could be added to the exhaust system. Additionally, the installation of Boom Mats, would help reduce in-cabin noise.

    AMJEFF

    Good Answer (0) (0)

Question Resolved

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Customer Reviews (72) Write a Review

Overall Rating 4.7

out of 5 stars

Installation Time:Afternoon

Installation Cost:0-$100

  • Loudness / Volume 4.642857 4.6
  • Exhaust Note 4.785714 4.8
  • Fit & Finish 4.814286 4.8
  • Bang For Your Buck 4.628572 4.6



  • 5/5

    Installation Time: Less than 1 Hour

    April 20, 2014

    Quick install

    Minimal time with excellent return on investment. Love the sound, classic muscle exhaust note.

    Jim2013

    Year: 2013 Submodel: Boss Idaho

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    April 07, 2014

    Good buy

    Installed the exhaust myself in around an hour with no experience and basic tools. Looks and sounds good. No complaints.

    Joseph08law

    Year: 2013 Submodel: GT

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    March 09, 2014

    2014 CS/GT

    Easy to install and has a great exhaust tone. Just what I was looking for. it took about an hour to install by myself with my basic tools and a floor jack.

    n2mygt

    Year: 2014 Submodel: GT Richmond, VA, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    April 29, 2013

    Verry Happy owner

    It took me awhile to pick out which set I wanted for my car. I'am completely satsfied with my American Thunder 44 serious mufflers and I would recomend them to anyone that owns a newer mustang gt.

    bill2014

    Year: 2014 Submodel: GT

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    March 25, 2013

    Flowmaster american thunder classic (13 gt)

    Verry aggressive sound. Great low rumble at idle. Sounds more like an old 68 fastback now. Real head turner. Every time i turn the key i get chills. The best exhaust to buy if you like that classic style. Go retro!

    Jackson21

    Year: 2013 Submodel: GT Pell City, AL, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    January 23, 2013

    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 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!!

    SELENE2013

    Year: 2013 Submodel: GT Beaverton, OR, USA

    Helpful (6) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    April 08, 2013

    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 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 Submodel: GT

    Helpful (4) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    June 11, 2013

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

    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 Submodel: GT Alabama

    Helpful (2) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    November 10, 2012

    Flowmaster American Thunder Classic Axle-Back

    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 Submodel: GT Houston, TX, USA

    Helpful (3) (1)

  • 3/5

    Installation Time: Afternoon

    March 03, 2015

    Unpleasant sound

    This is my second Flowmaster axle-back system. The first one was a Force II. Loved it. However, this American Thunder system is a quantum leap in terms of noise. It's very loud, which I would have been OK with had it not been to an overpowering DRONE around 2000 RPM's. The drone is very pronounced and I'm not happy. I'm considering putting the stock system back on it. In fairness I do like the exhaust note under full throttle. It's great! Sadly it doesn't make up for the painful resonance at cruising speed.

    Hoop

    Year: 2014 Submodel: GT Rossville, GA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    December 24, 2014

    Sound great, super easy install.

    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 Submodel: GT Louisiana, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    September 09, 2014

    Keep that true mustang sound!!!

    The American thunder axel back is awesome. I've had a 14 GT for a month and a half and couldn't wait to put an exhaust on. I was between the pypes pipe bomb, the flowmaster outlaw and the American thunder. I did a lot of research and listened to a lot of you tube videos cause I had never heard any of these three axel backs in person. Let me just say if your between those three just stop your research and get the American thunders. They sound unbelievable. They really keep the mustang sound just make it deeper and louder. The installation was a piece of cake with an extra pair of hands and a lift. About fifteen minutes. They have an awesome idle and they don't make it easy to keep your foot off the gas. There is a slight drone at 2000 rpm but with a manual you can adjust whether you want to hear it or not. Personally I kind of like it. Makes me feel like I'm actually in a mustang. Fitment was perfect and I'm actually starting to turn heads. And you don't have to worry about waking the neighbors its not obnoxious and wont attract the wrong kind of attention. I highly recommend these axel backs. Thanks AM for helping me with my first mod.

    Baller31

    Year: 2014 Submodel: GT Asheville, NC, USA

    Helpful (1) (0)

  • 3/5

    Installation Time: Afternoon

    June 08, 2014

    too much drone

    The exhaust note was awesome and the loudness was good, but the droning inside the car was unacceptable. It occurred even on light acceleration, so just poking around town was noticeable (though tolerable). But highway driving would give you a headache! Some guys don't mind the droning, but it bothered my middle-aged sensibility. Think carefully before forking over the money since you can't return it. Afterward, I spoke to the sales rep. He was very helpful and steered me toward a Borla. Should have talked to him first.

    wwsGT

    Year: 2014 Submodel: GT Carlisle, PA, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    May 13, 2014

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

    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 Submodel: GT Columbus, OH, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    August 15, 2013

    Vrmmmmm

    When I purchased my 2013 I originally wanted Borlas. After seeing the price, I decided to go with the American Thunders. Install was very easy, they fit perfectly and the exhaust tip fills the hole nicely. The sound is incredible when you start it up and brings a smile on my face every time and makes all the other people wish they had the car. Droning at cruising speed is deafening at first, but after 500-800 miles it goes away and is acceptable. Can't go wrong with Flowmasters. Of course American Muscle shipped this quickly!

    Jtrain

    Year: 2013 Submodel: GT New Jersey

    Helpful (1) (0)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    June 25, 2013

    Great Sound!!!

    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 Submodel: GT

    Helpful (3) (2)

  • 5/5

    Installation Time: Less than 1 Hour

    June 18, 2013

    Perfect Choice

    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 Submodel: GT El Paso, TX

    Helpful (1) (0)

  • 3/5

    Installation Time: Afternoon

    February 16, 2013

    2013 gt flowmaster AT classic axle back

    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 Submodel: GT Lebanon OH

    Helpful (2) (5)

  • 5/5

    Installation Time: Less than 1 Hour

    February 15, 2013

    Awesome

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

    Jojodanca

    Year: 2013 Submodel: GT

    Helpful (1) (4)

  • 5/5

    Installation Time: Less than 1 Hour

    September 26, 2013

    If its too loud... your to old!

    My daughter says she can hear it in the shower with the water running. My friend says it shakes the walls in my basement. I don't know what my neighbors think, but it makes me smile every time I open her up . And someone comments on the sound as soon as I start it up. 5.0 rocks and should be loud. Fast and loud...... watch out camero's. Ford nailed it!

    Chewy50years

    Year: 2014 Submodel: GT Michigan, USA

    Helpful (0) (1)

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