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

Item 18422
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      Review & Installation 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.

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • 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

      MPN# 817516

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (100+)

      Write a Review

      Ratings Summary

      4.8 out of 5 overall rating from 100+ customers

      Installation Time: Afternoon

      Installation Cost: 0-$100

      • March 25, 2020

        5 2012 GT - James12121 Installation Time: Less than 1 Hour

        Great sound

        Very easy to bolt on takes 5 min per side... looks good with the 4inch exit chrome piece over the stock 3inch... made my stock 5.0 much more louder cruising speed you can still hold a conversation but its close.. i may switch to a different after headers and xpipe. Good product always a flow master fan

        Helpful (0)
      • January 14, 2020

        5 2011 GT - GaryP Installation Time: Full Day


        My flowmaster outlaws sound great and the 4 inch tips look great

        Helpful (0)
      • December 16, 2019

        5 2011 GT - PRColo Installation Time: Less than 1 Hour

        Great product

        A big diff Awesome sound with great fit. Look great in my GT

        Helpful (0)
      • December 10, 2019

        5 2012 Boss 302 - kjbs5 Installation Time: Less than 1 Hour

        Flowmaster outlaws

        I replaced my roush mufflers with the outlaws I am more than pleased. They sound great it makes the Boss sound really good especially with kooks long tube headers.

        Helpful (0)
      • September 30, 2019

        5 2011 GT500 - Outlaws Installation Time: Less than 1 Hour

        Amazing Sound WOW

        I put these on by myself in about an hour without jacking up the car and I’m a bigger dude. They really woke up my 11’ GT500 and sound amazing

        Helpful (0)
      • March 26, 2019

        4 2012 GT - Ben Installation Time: Less than 1 Hour

        Sound good.

        Honestly I feel my Roush axle backs are louder then these. But the Roushs were starting to split at the welds so wanted something louder but doesn’t sound like it. Sounds good but not the same bark as the Roush ones at full throttle. Still have stock exhaust from axle forward so on to those next!

        Helpful (1)
      • March 22, 2019

        5 2011 GT - ChrisL Installation Time: Afternoon

        Flowmaster Outlaw

        This is exactly how your V8 should sound, this exhaust is exactly what I wanted. The install took me around 2 hours with only a jack, jack stands and hand tools, if I can do it alone, anyone can do it.

        Helpful (0)
      • January 21, 2019

        5 2012 GT - JaydenF Installation Time: Less than 1 Hour

        Love it

        It’s very loud and has an amazing tone, people always ask me what I did to it!

        Helpful (2)
      • December 28, 2018

        5 2012 GT - BigMack Installation Time: Less than 1 Hour

        Bang For Your Buck

        This exhaust is one of the loudest ones you can get for the GT. Has a nice mean growl and you will def break some necks in the process. It only gets better when you have a intake. Anyone can do it, don’t take it to a shop, just need an jack, simple hand tools, and some lube.

        Helpful (4)
      • December 11, 2018

        5 2011 GT - CookieMonster Installation Time: Shop Install Installation Cost: $250-$500

        That roar you've been looking for

        Amazing exhaust note, just a really loud cabin drone around 2k rpms, either get used to it, break it in, or get sound proofing.

        Helpful (4)

      Questions & Answers (21 answers)

      5 Top Rated Questions


      • These will weight roughly 24lbs and will be roughly 35.33 X 14.67 X 15 in size.

      Helpful (2)

      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

      Helpful (2) Show 1 more answer

      Is there any way to lessen the exhaust drone at around the 2k RPM mark when its really bad on the highway?? Currently running straight pipes w/ cats and factory headers.

      • Unfortunately we do not currently offer a resolution for the drone. The best thing to do is switch to a quieter exhaust as this could help lower the drone you experience at 2000 RPM.

      Helpful (1)

      I live in California and I drive a 2013 Boss 302. I'm wondering if this Exhaust system will keep up with the new sound regulations?

      • None of our exhausts currently have the decibel levels so it is unknown if they are in compliance.

      Helpful (1)

      I’m seriously interested in installing this on my 2011 gt, ragtop. It would be the 1st mod done. Will this require any tuning, or is this simply a drop n swap?

      • The Flowmaster Outlaw Axle-Back Exhaust is a completely bolt-on exhaust system. This exhaust does not require a tune or additional modification for a complete installation. 

      Helpful (1)
      10 More Questions
      What is the difference between these and the 13-14 model. Would the 13-14 not fit a 2012 Boss 1 answer
      Is there a way to change the tips for 4.5 inch tips? 1 answer
      Would this exhaust be too loud for a convertible? 1 answer
      If I get the pypes true dual conversion for my 2010 V6, will this axel-back fit? 1 answer
      Will this fit on a 2011 V6? 1 answer
      If I get the right pipes on my 2010 mustang will I beable to just put this exhaust right on? 1 answer
      do you have to make computer adjustments after installation 2 answers
      Any HP gains? Are there any noticeable HP gains? And will I benefit from a retune after installation? 2 answers
      Which axle back muffler system is louder the flowmaster outlaw series or the heartthrob muffler delete system for 2012 Mustang GT ? 2 answers
      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.... 1 answer

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (2) Muffler assemblies
      • (2) 3/8" Hanger Keepers

      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

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