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Flowmaster American Thunder Classic Axle-Back Exhaust (11-12 GT, GT500)

AmericanMuscle no longer carries the Flowmaster American Thunder Classic Axle-Back Exhaust (11-12 GT, GT500). Please check out 2010-2014 Mustang Axle-Back Exhaust for an updated selection.
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Features, Video & Details

  • Aggressive Flowmaster Classic 40 Series Sound
  • Polished Stainless Steel 4" Tips
  • Durable 409 Stainless Steel Construction
  • Includes Two Flowmaster Mufflers
  • Fits 2011-2012 GT and 2011-2012 Shelby GT500 Mustangs

Review & Installation Video

Review & Install Video

Hey everyone I’m Justin with AmericanMuscle.com and I’m taking a look at Flowmaster’s American thunder classic axle-back for your 2011 and newer Mustang GT. The American Thunder series axle-back is designed to give your Mustang that iconic Flowmaster sound, while giving you a little more horse power at the rear wheels. The system is constructed from durable 3 inch, 16 gauge aluminized tubing, and features 2 40 series chambered mufflers, everything is finished off with two 4 inch polished tips embossed with the classic Flowmaster logo. Now the installation itself should only take you about an hour using standard hand tools. Now lets see how Flowmasters American Thunder sounds compared to your factory exhaust.

Classic Flowmaster Sound. Give your 2011-2012 Mustang GT or GT500 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 Classic 40 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.

Application. This Flowmaster American Thunder Axle-Back exhaust system is designed to fit the 2011-2012 5.0 Mustang GT and 2011-2012 5.4L Shelby Mustang GT500 for both great looks and great sound.

Fitment: 2011 2012 Details

MPN# 817496

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

What's in the Box
Hardware included:
  • (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: 2011-2012 Mustang GT & 2011-2012 GT500
Will it fit my Mustang?

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Questions & Answers (4)

4 Top Rated Questions

Will this fit a 2014 5.0?

  • This Flowmaster American Thunder Axle-Back exhaust system is designed to fit the 2011-2012 5.0 Mustang GT and 2011-2012 5.4L Shelby Mustang GT500 only.

Helpful (0)

I own a 2013 v6. Will these fit? Thank you for your time and assistance.

  • Unfortunately, this Flowmaster American Thunder Classic Axle-Back Exhaust is specifically designed for use on 11-12 GT and GT500 model Mustangs, so it will not fit your 2013 V6.

Helpful (0)

i have the outlaw series cat back will these mufflers bolt up to the outlaw exhaust the outlaw series mufflers are too loud with the long tube headers

  • Yes, The piping will step down to allow for the axle back to be interchanged from the Flowmaster Outlaws to the Flowmaster American Thunder Classic Axle-Back Exhaust.

Helpful (0)

Rear Valance I am thinking about getting Flowmaster American Thunder Classic Axle-Back Exhaust (11-12 GT, 11-12 GT500), but will I also need to change the rear valance as well? I have a 2012 GT /CS with stock everything now and was just wondering if I would have to do more mods to get the system. Any help would be greatly appreciated!

  • Your current rear valence set up will be fine, as the single outlet mufflers will fit thru the same space as your existing mufflers. Had you gone for the quad set up (2 outlets per muffler), then you would need the gt500 rear valence.

Helpful (0) Show 2 more answers
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Recommended For You

Customer Reviews (67) Write a Review

Overall Rating 4.6

out of 5 stars

Installation Time:Less than 1 Hour

Installation Cost:$100-$250

  • Loudness / Volume 4.442307 4.4
  • Exhaust Note 4.653846 4.7
  • Fit & Finish 4.692307 4.7
  • Bang For Your Buck 4.392157 4.4



  • 4/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    January 02, 2018

    Sound great

    These have the sound I was looking for, but they would not mate up to the 3” after market pipes in my Stang. I had to take to a custom shop and Pay $150 to have them welded on. Now they look good and sound great. Had Pype Bombs on it before and they were just way too loud.

    Jack99

    Year: 2012 Submodel: GT

    Helpful (4)

  • 5/5

    Installation Time: Less than 1 Hour

    November 04, 2017

    Sound Amazing

    These axlebacks slund amazing . Alot better than stock for sure

    JNich

    Year: 2011 Submodel: GT

    Helpful (3)

  • 2/5

    Installation Time: Afternoon

    October 10, 2017

    Damaged

    the flowmaters sent to me I received were damaged on the mounting flanges (huge flat spots) the packing was poorly done the mufflers were able to move freely I had to machine a die to rework the flange angle otherwise they would never had seated properly they are mounted with no leaks I shouldn't have to fix a product I paid hard earned money on...

    PHILIP

    Year: 2012 Submodel: GT

    Helpful (3)

  • 2/5

    Installation Time: Afternoon

    September 02, 2017

    Very loud mufflers

    These mufflers are rated as quieter but they are actually extremely loud. Going through residential areas I had to feather the gas pedal to make sure no cops would notice me. I had to add another set of mufflers in front of the differential to cut the noise down and they are still very loud. However, they sound good at idle and at WOT

    PierreP

    Year: 2011 Submodel: GT

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    June 08, 2017

    Very nice sound

    A beautiful sound that gives character to my Mustang

    BrunoC

    Year: 2011 Submodel: GT

    Helpful (3)

  • 5/5

    August 02, 2016

    There everything I though they be

    I love the Flowmaster American classic if you like deep rich sound the Flowmaster is the one for you putting this puppy's in is just about a 1hr job getting the mufflers out of the hangers is the hardest part but the fight is well worth it if by them you will injoy

    One909

    Year: 2011 Submodel: GT

    Helpful (4)

  • 5/5

    July 06, 2016

    WOW!!!! Amazing sound

    I was always a fan of the fox body Flowmaster sound! So when I got these for my 2011 GT500 that's what I was hoping for and WOW!! Love the sound all around, sounds great starting up, at idle and it has a monsterous sound under acceleration! So happy I got these!!!

    EricJ

    Year: 2011 Submodel: GT500

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    March 18, 2016

    Get it. You'll love it.

    These sound great. Loud when you want it. Quiet when cruising. Easy install.

    NEMO

    Year: 2012 Submodel: GT

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    February 22, 2016

    pmo

    I put the flow master exhaust om my 2011 mustang gt 5.0 it sounds good and fast I would recommend into all my mustang buddys

    paul

    Year: 2011 Submodel: GT Zanesville Ohio

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    October 26, 2015

    Flow maser

    Great product, looks great and sounds awesome. Fit was great also

    JJ

    Year: 2012 Submodel: GT Chattanooga

    Helpful (3)

  • 2/5

    Installation Time: Less than 1 Hour

    May 14, 2015

    Not What I Wanted

    I have a 12 with an automatic. At 1700 to 2100rpm the drone is so loud you can't ave a conversation in the car. Shift point and interstate speed falls right in this drone range. At cruise speeds around town the deep rumble is awsome and the idle rumble takes me back to the day. I just can't handle the drone so I'm planning on replacing these mufflers with something with less drone. Flowmaster missed it with these mufflers. I have had two other cars with Flowmaster mufflers and enjoyed them both but not these.

    Manon

    Year: 2012 Submodel: GT Louisville KY

    Helpful (5)

  • 4/5

    Installation Time: Afternoon

    October 21, 2014

    Loud, Deep, Powerful

    I will say the Thunder Classic is everything as promised -- loud, deep, and powerful sounding; however, I gave it an overall lower rating (4 stars) and average exhaust note rating (3) because of the very intense and relentless drone at all speeds & rpms. There really is no point at which your ears get a rest from the drone, so it just takes some getting used to, but man does it sound great when you jump on it !!! **It is also important to note that I have this exhaust paired with a JBL CAI and bama tune, so I don't know how that is potentially effecting the intense drone described above.

    Bigstick

    Year: 2012 Submodel: GT

    Helpful (4)

  • 5/5

    September 05, 2014

    Make your coyote bark.

    Just installed the Flowmaster American Thunder Classic Axle-Back Exhaust on my 2012 GT. The first start was excellent, that raspy growl can't be beat. Took longer than an hour, but that's Ok. I removed the stock mufflers and brackets as one piece. Makes it easier to wrestle the rubber over the nub on the hangers. The install was super easy, plenty of room to reach the bolts. A lot lighter than the stock pieces. Follow the instructions and its cake.

    Yokmoni

    Year: 2012 Submodel: GT Illinois

    Helpful (3)

  • 5/5

    Installation Time: Afternoon

    August 24, 2014

    sounds like car looks

    very happy with product. loud, but not too over the top. looks a lot better than stock. took 3 hours, with a few tools. car not the same with stock exhaust.

    rick44444

    Year: 2011 Submodel: GT phila. pa.

    Helpful (3)

  • 4/5

    Installation Time: Less than 1 Hour

    June 09, 2014

    These axlebacks have a nice growl!

    Worth the money, sounds great, the drivers side tip was a little off center for the drain hole for condensation but other than that it all looks good and has the growl I was looking for! Thanks!

    mergasmerga

    Year: 2012 Submodel: GT Junction City, KS, USA

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    September 25, 2013

    Awesome sound

    Awesome sound I'm currently running an off road H-pipe with these axlebacks.Deep sound with no rasp, and there is minor drone then what everyone else is saying. A must buy for your stang!

    Lozo5OH

    Year: 2012 Submodel: GT West Palm Beach, FL, USA

    Helpful (6)

  • 5/5

    Installation Time: Less than 1 Hour

    August 15, 2013

    Not too loud, great mean rumble, just what I was looking for!

    Great sounding exhaust. I was looking for something that was loud enough for people to hear but not so loud that I cant hear myself think on the highway. This was the perfect exhaust for that. looks great, sounds great, and its affordable. I recommend it!

    liquidsilver

    Year: 2011 Submodel: GT Southwest Mo

    Helpful (3)

  • 2/5

    Installation Time: Afternoon

    July 19, 2013

    Product gives too much interior drone

    I expected a great exhaust note based on my 2008 GT that had the same system. The exterior sound on my 2011 is excellent but the interior sound is unbearable. I am switching to a Ford Racing GT500 Axle back hoping to tone down the interior drone. If not, its back to stock.

    Lowball

    Year: 2011 Submodel: GT North Carolina, USA

    Helpful (4)

  • 5/5

    Installation Time: Less than 1 Hour

    May 15, 2013

    Flowmaster American Thunder Classic Exhaust 2011 GT

    The fit was flawless; had to remove the muffler clamp from the stock mufflers, but it wasn't any problem. They are spot welded to the pipe; just bend the strap back and forth until it breaks and reuse the clamp on the new mufflers. The sound is really great - pretty much what I expected and what the car should have sounded like in the first place. The other reviews mentioned a drone at around 2000 rpm - it's there alright, especially when under load. It can drown out the sound system, but I'm fine with that. Now I drive with the windows down just to hear the sweet thunder. Great product, just wish it wasn't priced so high.

    MikieLikesIt

    Year: 2011 Submodel: GT Crowley, TX, USA

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    May 13, 2013

    WOW. Thats what a 5.0 should sound like

    Read directions first-LOL. Very easy install when you unbolt cross member. Make sure you lube hangers and its a sinch. Very nice fit. Very agressive at idle, sounds very old school.Crusing is very tolerable. Highway is tame until you hit the gas. I didnt really here the drone at 2000 rpm. If you have a stick, its very hard not to rev the rpms all the time. wow amd I happy with this purchase. Nice job FLowmaster.

    sfistang

    Year: 2011 Submodel: GT Temperance, MI 48182, USA

    Helpful (3)

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