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

100+ Reviews
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  • Item #18422
  • MPN# 817516

  • Market Price $487.00
  • You Save 12% ($56.03)
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Product Videos Customer Photos
  • 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
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

Most Helpful Reviews

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. ...

Read More
Helpful (1)


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 ...

Read More
Helpful (1)

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

Review & Install Video

Hi I’m Justin with, 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.

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11 Questions / 15 Answers

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


  • The Flowmaster Outlaw axle-back is as loud as you can get with only axle-back replacement. There is no muffler on this system, it's basically a straight pipe. I'm not sure but I think the shape of the tubing may give it some sound quality. When I bought this set I though it was too loud on the highway but now I'm getting used to it.


    Good Answer (0) (0)

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will they fit my2013 v6 mustang


  • I dont think so these exhaust are for V8 only


    Good Answer (4) (0)

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How loud is this exhaust compared to slp loudmouths axleback? I'm stuck between the two. I definitely want loud but not obnoxious loud. And when I say loud I mean outside loud. It's ok to be moderately loud inside but nothing vibrating my ears. Also I like the deeper growl sound over the high pitch nascar sound. Thats why I decided against rousch axlebacks. Hoping to get some good feedback. As I do plan on ordering my exhaust from you guys. I have watched numerous videos of just about any exhaust imaginable for the new 5.0 If theirs some other exhaust option that you think would better suit me I'm still open for suggestions. If it helps any on a scale of 1-10 with 10 being loudest I'm looking for 8 and half to 9. Thanks guys.


  • Slp's sound like junk! Anyone who has them if u listen to them when they take off at a light , all u hear is raspy obnoxious sound & u think the guy is doing 100 mph! But he's doing 25! Slp's come on GM's , their not made for fords to sound good. Buy the flowmasters!!! U won't be dissatisfied! Magnaflows are a waste to so don't waste your money. Go with the flowmasters.. you'll be happy


    Good Answer (4) (0)

Show 3 more answers Question Resolved

Dose this part fit on my Mustang GT 2010 ?! i'm so confused.


  • Not this particular axle-back. Below, I've attached the link for the Flowmaster Outlaw Series Axle-back that will fit on your 2010 GT! Give us a call if you have any further questions!


    Good Answer (0) (0)

Show 1 more answer Question Resolved

can some one give feed back on sound compared to stock 2012 GT 500 want louder more aggressive deep sound


  • Yes, the sound is on the 2012 GT500 is more deep, bolt, and agressive than the stock SVT mufflers. I recommend this product for your GT500.


    Good Answer (1) (0)

Show 2 more answers Question Resolved

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.


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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 4.837607 4.8
  • Exhaust Note 4.854701 4.9
  • Fit & Finish 4.683761 4.7
  • Bang For Your Buck 4.863248 4.9

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

  • 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) (0)

    • Response from AmericanMuscle

      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) (0)

  • 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: Mark


    Year: 2012 Submodel: GT Pasadena, CA, USA

    Helpful (9) (1)

  • 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) (0)

  • 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) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    July 22, 2012

    Amazing Sound!!

    These Mufflers Completely woke up my 2013 5.0. They sound incredible! I definitely recommend these to everyone. I can hear the power between every shift! only complaint is that they were a little nicked up when i received them.All in all great product. I buy everything for my Coyote from AM!!


    Year: 2013 Submodel: GT Ohio, USA

    Helpful (2) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    April 11, 2012

    2012 GT 5.0 axle back flowmaster outlaws

    Install only took me 45 minutes for both sides. The sound is amazing over the stock mufflers, but there is a slight drone at highway speeds. I usually shift gears, crack the window, or turn up the radio if it bothers me which normally it doesnt.


    Year: 2012 Submodel: GT El Paso, Tx

    Helpful (2) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    February 11, 2012

    this product sounds mean

    i would recommend this exhaust for everyone. it sounds good and really loud


    Year: 2012 Submodel: Boss

    Helpful (2) (0)

  • 4/5

    Installation Time: Less than 1 Hour

    November 19, 2011

    very agressive exhaust system

    I purchased these because I got a really good deal on them and decided to change up the sound a little. My previous setup was a lethal o/r x pipe and Roush. It sounded good but the tone wasn't really there. I put these on and now it has a deeper idle but isn't as loud as the Roush when you get on it. They are still really loud but better tone. The only downside is that they do drone a little but Idk if they do or not without an x pipe, doesn't bother me though so im happy with these.


    Year: 2011 Submodel: GT columbus, ohio

    Helpful (2) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    October 14, 2015

    Neighbors will hate me!

    If you are looking for an exhaust that will make everyone mad at 2am in the morning, look no further!


    Year: 2012 Submodel: GT Florida

    Helpful (1) (0)

  • 5/5

    July 25, 2012

    Great sound

    These flowmasters are awesome, and they are loud. They really give my stang the muscle car sound it should have. Everyone I know gives it a two thumbs up. I drove a 5.0 with The Roush mufflers and debated on getting them; however the flowmasters were on sale. I'm glad i got them, in my opinion, these sound way better.


    Year: 2011 Submodel: GT Texas

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    July 21, 2012

    Great product!

    The Flowmaster Outlaw Series Axle-Back Exhaust were very easy to install. Excellent sound and they added an overall great look to my 5.0 Mustang.


    Year: 2011 Submodel: GT Savannah, GA, USA

    Helpful (1) (0)

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