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Flowmaster Outlaw Series Axle-Back Exhaust (11-12 GT, 11-12 GT500)

Market Price $509.99 You Save 13% ($67.02)
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  • Item 18422
  • MPN# 817516

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Features, Video & Details

  • Super Aggressive Flowmaster Outlaw Sound
  • Durable 409 Stainless Steel Construction
  • 2.75" Mandrel-Bent Tubing
  • 4" Polished Stainless Steel Tips
  • Includes Two Flowmaster Outlaw Mufflers
  • Fits 2011-2012 GT, Boss and 11-12 Shelby GT500

Review & Installation Video

Review & Install Video

Hi I’m Justin with AmericanMuscle.com, and I’m taking a look at Flowmaster’s outlaw series axle back for your 2011 and up Mustang GT. The outlaw series is Flowmaster’s most aggressive system thanks in part to the straight through, race oriented style mufflers. The result, a super aggressive tone that’s sure to get you noticed. The system is constructed from durable 2 and 3 quarter inch 16-gauge steel, leading straight through these outlaw style mufflers. The cheery on top are these 4 inch polished tips, embellished with a Flowmaster logo. A simple bolt on installation here guys, should take you no more than an hour. Let’s hear how Flowmaster’s outlaw style axle back measure up to the stock exhaust.

Super Aggressive Flowmaster Sound. Give your Coyote powered Mustang that unmistakable Flowmaster sound with the Outlaw Series Axle-back exhaust system from AmericanMuscle. This system improves exhaust flow using Flowmaster's race-oriented style Outlaw mufflers for that super, aggressive exhaust note your high powered Pony deserves.

Stainless Steel Construction. Constructed from durable 2.75" 16 gauge 409 stainless steel tubing for it's corrosion resistant properties the Flowmaster Outlaw Axle-back features two race-oriented mufflers with massive 4.0" diameter polished 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.

Application. This Flowmaster Outlaw Series Axle-back exhaust system is designed to fit the 2011-2012 GT, Boss and the 2011-2012 Shelby GT500 Mustangs for both great looks and great sound.

Fitment: 2011 2012 Details

What's in the Box
  • (2) Muffler assemblies
  • (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: 2.75" Tip Size: 4.0"
Muffler Type: Straight-through Fitment: 2011-2012 GT, Boss and Shelby GT500
Will it fit my Mustang?
  • Boss 302 - 12
  • GT - 11, 12
  • GT500 - 11, 12

People Who Bought This Item Also Bought

Most Helpful Reviews

Hear this Pony Roar!!

It was harder and took longer taking off my Stock Exhaust than it did Putting on these OutLaw exhaust. Went on with no Problems and fit Perfectly all with in about an hour... After they are installed just ...

Read More
Helpful (1)

By the gray beard of Zeus, this exhaust...

Is amazing. For the price, you cannot beat the sound. No youtube video will do this axleback justice. Installation was a pain in the --- because I'm a driveway mechanic, and doing this on ramps was a little ...

Read More
Helpful (1)

Overall Rating 4.8 out of 5 stars
Read All 100+ Reviews

Customer Photos (21) Submit Your Photo

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12 Questions / 10 Answers

Ask a Question

How far does the tips extend out the rear of the car? I was wondering how far does the tips extend out the rear of the car compared to stock?


  • Not much at all it's perfect


Show 1 more answer Helpful (1)

What is the difference between these and the 13-14 model. Would the 13-14 not fit a 2012 Boss


  • The rear lower valance on the 2013-2014 models is different from that on the 2011-2012 model Mustangs. These are specific for the 2011-2012 model Mustang rear end.


Helpful (0)

do you have to make computer adjustments after installation


  • No. I have them on my 2011 GT500 and they sound great. If you have it mapped you wil probably pick up a few more horsepower but they're good on their own.


Show 1 more answer Helpful (0)

Any HP gains? Are there any noticeable HP gains? And will I benefit from a retune after installation?


  • Normally, You gain 3-8 HP for these, but nothing noticeable. Still an excellent choice for exhaust, by far one of the best.


Show 1 more answer Helpful (0)

Which axle back muffler system is louder the flowmaster outlaw series or the heartthrob muffler delete system for 2012 Mustang GT ?


  • I have the Outlaw exhaust on my Shelby and I love them. They're loud and throaty without being too loud. Great bang for the buck!


Show 1 more answer Helpful (0)

Compatible w/ Magnaflow Comp Cat-Back? I currently have the Magnaflow Competition Cat-Back system installed on my 2012 GT. I've been looking at the muffler delete axle backs; but, something about these Flowmasters grabbed my attention. They just sound like the perfect amount of "old school" rumble and seem to make the 5.0s growl. My questions are: will these bolt up to the Magnaflow pipes? And, are they something I should really consider--the (Flowmasters) appear to be more "muffler delete" than what the Magnaflow mufflers have, will it give me a more aggressive/old school sound? Or will I be out $400 without changing my exhaust sound....


  • If you already have the Magnaflow Comp Catbacks, you really don't need these muffler delete axelbacks. Sure it'll give you more "rumble" but I ask why since the Magnaflow Catbacks like I have installed on my 2010GT are plenty loud enough for my liking. IMHO.


Helpful (0)

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Customer Reviews (100+) Write a Review

Overall Rating 4.8

out of 5 stars

Installation Time:Afternoon

Installation Cost:0-$100

  • Loudness / Volume 4.854962 4.9
  • Exhaust Note 4.862596 4.9
  • Fit & Finish 4.694656 4.7
  • Bang For Your Buck 4.854962 4.9

  • 5/5

    Installation Time: Less than 1 Hour

    May 17, 2016

    Hear this Pony Roar!!

    It was harder and took longer taking off my Stock Exhaust than it did Putting on these OutLaw exhaust. Went on with no Problems and fit Perfectly all with in about an hour... After they are installed just start that Coyote Motor and listen to it Rumble, you will have every body braking their necks trying to see who's car this is!!! #PurePantyDropper


    Year: 2012 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    April 07, 2014

    By the gray beard of Zeus, this exhaust...

    Is amazing. For the price, you cannot beat the sound. No youtube video will do this axleback justice. Installation was a pain in the --- because I'm a driveway mechanic, and doing this on ramps was a little difficult. Having to twist and maneuver the old mufflers out of the backets was a pain. However, once the stockers were off, the rest took no more than 20 minutes. Guys, the noise... It's thunder. Idling, it rumbles. Under throttle, it screams. Cruising at 1500, it blurbles. Be warned, there is drone at 70mph@ 2000rpm. If you do highway driving, have some music prepared. I have 2 friends with GT500 mufflers and Roush axlebacks, neither sound near as good. If you get this, you will NOT be disappointed. Also should note I docked a star on finish because a few large parts of the black paint had chipped away in shipping. Other than that, could not be happier.


    Year: 2014 Submodel: GT Indiana

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    March 31, 2014

    Great Sounding Exhaust

    I'm very pleased with the Outlaw system, easy to install (only an hour), and a great sound that draws a lot of attention to my Shelby GT500.


    Year: 2011 Submodel: GT500 Rincon, GA 31326, USA

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    November 15, 2013

    Loud and Sound Amazing!

    I received these exhaust yesterday and couldn't wait to install them. It took me roughly two hours with only one jack (had to do each side separately). The exhaust were simple to install. The only problem was getting the left exhaust in one of the hangers. First time I started the car it was like a new mustang! I revved the engine and wow... these are LOUD. I got chill bumps the first time I heard it! They have that nice classic muscle car tone and rumble I was looking for. At around 2k rpm there is a slight drone, but I have had Flowmasters before and expected some drone. It is not very noticeable unless you are used to stock exhaust. I don't mind it at all. A little drone is not a big deal when you have great sounding exhaust like these! If you are looking for loud, deep, and aggressive sounding exhaust with some classic muscle car rumble these are what you are looking for! These exhaust with definitely get you noticed and turn heads everywhere you go. They sound amazing and are worth every penny! Thank you AM!!!


    Year: 2011 Submodel: GT Little Rock, AR

    Helpful (1)

  • 4/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    June 27, 2013

    Great sound but some drone

    These have the strong sound I was looking for, and I am well pleased on that point. The only issue with these is there is a strong drone at 2000-2100 rpm's, that is somewhat of an issue. You need to shift to keep it out of this range when you maintain a constant speed. The biggest problem is in fourth gear, so I have to shift up into fifth.


    Year: 2012 Submodel: GT500

    Helpful (1)

  • 5/5

    Installation Time: Weekend

    June 20, 2013

    Totally Worth It!

    I'm not a technical person when it comes to cars, I spent about 90 minutes changing these out all on my own and I was proud and excited when I heard them on my 2012 GT!! Only thing I wasn't too pleased was that there were no clamps in the box so I had to use the stock ones! Still totally worth the money!


    Year: 2012 Submodel: GT San Jose, CA, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    June 13, 2013

    Awesome Sound!

    This item was easy to install. Took less than an hour to do with just a socket and ratchet. It has a great sound that's aggressive sounding but not too loud. A little drone at 2000rpm but not bad. This was money well spent. I love them.


    Year: 2011 Submodel: GT500 Modesto, CA, USA

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    June 11, 2013

    Sounds like a Shelby should!

    Hardest part was removing stock exhaust. Perfect fit !


    Year: 2012 Submodel: GT500 Florida, USA

    Helpful (1)

  • 4/5

    Installation Time: Less than 1 Hour

    April 08, 2013

    Very Loud

    If you want subtle, then look elsewhere. The drone is exceptionally bad, but definitely worth it. I compromise by driving a little faster on highway. The sound this makes is incredible. It makes the 5.0 sound the way it should have sounded from the factory. The product had no scratches and was easy to install, although the instruction are worthless.


    Year: 2012 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    March 30, 2013


    I purchased these axle-back Flowmasters they are Awesome the videos do not do them any Justice. The sound it just what this muscle car needed ,It took lees than 30 minutes with ramps and 13mm socket easy to adjust and the rumble is just outstanding thank you American Muscle for the prompt delivery,I definitely recommend these mufflers


    Year: 2012 Submodel: GT San Diego, CA, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    January 22, 2013

    Newborn Beast

    Exhausts are almost a little too loud, but that's a good thing in my book. It really makes your V8 sounds like a BIG V8. Setting off car alarms as you drive by. Cold starts are ridiculously beefy sounding. Outlaws are amazing!


    Year: 2012 Submodel: GT Imperial, CA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    October 11, 2012

    Excellent Sound!!!

    My GT500 sound like a real muscle car with these set of Outlaws from Flowmaster. Sound is exquisite, bolt, and just more agressive than EOM. I shared the joy of others, Definetely the sound I was looking for. I recommend this system to anyone looking for a more agressive sound in any stang.


    Year: 2012 Submodel: GT500 Lawton, OK, USA

    Helpful (1)

  • 5/5

    October 09, 2012


    Quick delivery and no defects noted in the muffles Installation (by myself) was not too bad though the instructions were not completely accurate for me (neither side would slide off the front hangers like the instructions stated so I unbolted the hanger bracket on the passenger side and loosened the bracket on the driver side to get the clearance needed to get the factory muffles off the hangers). Hardest part of the installation was removal of the driver side factory muffler. Now that I know how to deviate from the instructions, installation would easily be less than an hour (took me almost an 1 1/2 hours, mainly because of problems with the driver side). As many have said, the videos do not do the sound of the outlaws justice. Also as stated, there is a drone around 2k rpms. They are actually louder than I really wanted (because of the pesty neighbors) but I love that my 2011 GT now sounds like a muscle car should sound. Great product!


    Year: 2011 Submodel: GT Augusta, GA, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    July 28, 2012

    Flowmaster Outlaws on 2011 GTCS

    I was actually surprised how well this system fit. It went on with no problems and needed no adjustments at all. What I hear now is what you would expect a 5.0 Mustang to sound like.


    Year: 2011 Submodel: GT Columbus, OH, USA

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    June 04, 2012

    Best Sound yet on a GT500 in my opinion

    I replaced the stock axleback exhaust on my 2012 GT500 with the Outlaws and they are amazing. VERY loud and the drone is ok too except for a little around 2k rpm. Does tend to set off car alarms if you get on it though..... Installation was ok except I had to jiggle the drivers side around to fit properly as the hangers had been welded slightly off but no big deal.


    Year: 2012 Submodel: GT500 Chicago

    Helpful (1)

  • 4/5

    Installation Time: Less than 1 Hour

    March 08, 2012

    Flowmaster Outlaws

    Love the sound and overall product. Only one thing I did not like with the particular set I received is that the driver side tip was welded slightly to the right so the flowmaster emblem and drain hole are not exactly centered. I think it may be a factory defect for this particular set. Other than that, it's great.


    Year: 2012 USAF

    Helpful (8)

    • Response from AmericanMuscle

      It does sound like a factory defect as you mentioned. Please give us a ring and we can get you squared away with a replacement!

      Lisa , Content Specialist

  • 5/5

    Installation Time: Afternoon

    January 28, 2012

    Flowmaster Outlaw Axle-back for 5.0

    If you want an aggressive muscle car, one that sounds like a 60's era, you need these mufflers! I turn heads everywhere I go with this system. It is louder than stock and has a slight drone at 2K RPM's. It's not so bad that you can't have a conversation. One thing I particularly love about these is rumble when you let off the accelator and coast. Any video you see on the Internet with these does NOT do them justice! For the price especially, these are the best aggressive axle-backs on the market!


    Year: 2011 Submodel: GT Granbury, TX

    Helpful (8)

  • 5/5

    Installation Time: Less than 1 Hour

    September 26, 2012

    Very good, but not perfect.....

    I've had the FRPP GT500's, Kook's, Roush, and now the Flowmaster axlebacks, OVERALL, the Outlaws are my favorite! The GT500's and Kook's had better exhaust TONE at WOT, but were too quiet during normal driving. The Roush were the loudest at WOT, but sounded terrible, IMO. VERY raspy(4K and above)! They sounded good under normal driving, though. Now to the Outlaws. The tone is magnificent during normal driving; deep and the loudest out of the four I've had, but nothing obnoxious. The Outlaws aren't quite as loud as the Roush at WOT, but close. They're raspy as well, but not as bad as the Roush. There is some drone with the Outlaws, but nothing crazy. I actually like it! So, the Outlaws sound great under normal driving, semi-raspy at WOT(4K and above), but have the aggressiveness/loudness, overall, that I prefer. I wish there was an exhaust that had the loudness of the Outlaws, but no rasp at all like the GT500's/Kooks. However, with the stock cats and mid-pipe, the Outlaws are the best thus far! If you have any questions, feel free to email me: bruins17@gmail.com Mark


    Year: 2012 Submodel: GT Pasadena, CA, USA

    Helpful (9)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $100-$250

    April 01, 2013

    This is how I wanted my GT500 to sound!

    Like I said in the title- I wanted my '12 GT500 to sound more like the old days and my '66 and '69 Mustangs did. This'll do it! Wakes up the birds when you start up and gives you a nice tune when driving normal... but romp on the gas and that's when everything comes to life! The Outlaw axle backs are all I need to make those 550 horses come to life............ for now- of course!


    Year: 2012 Submodel: GT500 Whitesboro, NY, USA

    Helpful (3)

  • 5/5

    Installation Time: Less than 1 Hour

    July 08, 2013

    First start-up said it all

    This exhaust has a very mean sound which to me is best on start-up. I was in my garage and quickly put the pedal to the floor when I was showing a friend, and wow . . the walls simply shook. You will have quite a bit of interior noise and a rather loud drone at highway cruising speed, but a quick installation of some sound deadening in the trunk alleviated most of the issues so now it sounds very nice inside the car. My first installation of an exhasut on any car, and it was much easier than I expected.


    Year: 2012 Submodel: GT TX

    Helpful (2)

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