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Flowmaster Outlaw Series Axle-Back Exhaust (05-10 GT, GT500)

100+ Reviews
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  • Item #18423
  • MPN# 817511

  • Market Price $487.00
  • You Save 12% ($56.03)
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  • Super Aggressive Flowmaster Outlaw Sound
  • Durable 409 Stainless Steel Construction
  • 2.5" Mandrel Bent Tubing
  • 4" Polished Stainless Steel Tips
  • Includes Two Flowmaster Outlaw Mufflers
  • Fits 2005-2010 GT, Bullitt, and Shelby GT500
Super Aggressive Flowmaster Sound. Give your 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.

Quality Construction. Constructed from durable 2.5" 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 2005 to 2010 GT, Bullitt and the 2007-2010 Shelby GT500 Mustangs for both great looks and great sound.

Technical Note: Americanmuscle recommends adding the 2005+ Mustang 304 Stainless Steel Exhaust Hanger Kit from the drop down option above, to provide more strength, stability and a cleaner installed appearance. If you have a 2007 Mustang you may need the kit for correct installation.

Fitment: 2005 2006 2007 2008 2009 2010 Details

What's in the Box
  • (2) Muffler assemblies
  • (2) Clamps
Installation Info
Tech Specs
Axleback Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : Polished Stainless Steel
Piping Size: 2.5" Tip Size: 4.0"
Muffler Type: Straight-through Fitment: 2005-2010 GT, Bullitt and Shelby GT500
Will it fit my Mustang?
  • Bullitt - 08, 09
  • GT - 05, 06, 07, 08, 09, 10
  • GT500 - 07, 08, 09, 10

Most Helpful Reviews

You will love them...your neighbors won't!

I am not big on writing reviews but after installing these, I felt AM and Flowmaster deserved a review. First off, thanks AM for getting these to me in less than 24 hours, can't ask for much more than ...

Read More
Helpful (30)

So much better than....

I installed the Pype Bombs first and had a rough time with the fit. These are so much better fit and finish, these were easy to align and center in the cutouts and the sound is amazing!!! I think the tone ...

Read More
Helpful (11)

Read All 100+ Reviews
Overall Rating 4.9 out of 5 stars


Hey everyone I’m Justin with, and today we’re going to be breaking down the Outlaw series Axle-back from Flowmaster for the 2005-2010 Mustang GT. Flowmaster calls this their most aggressive View Full Transcript

Customer Photos (47) View All Photos

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12 Questions / 12 Answers

Ask a Question


echellon Year: 2005 Model: GT

  • Outlaw is plenty loud all by itself. If you want to amp it up try some long tube headers paired with an h pipe. But trust me they're good all by themselves

    Best Answer

    Cableguy500 Year: 2007 Model: GT500 Top 500 Contributor

    Good Answer (8)

Show 3 more answers Question Resolved

Need tuning? I drive a 2008 mustang gt and I'm wondering if I get these axle back exhausts will it affect my tuning in anyway or will I need tuning I don't have anything aftermarket like CAI, TURBOS, etc. just wondering Thanks

TOoCool Year: 2008 Model: GT

  • Axle-backs do not require a new tune once installed. Just bolt on and enjoy your new exhaust!

    LisaS Year: 1992 Model: GT

    Good Answer (0)

Show 4 more answers Question Resolved

Do the Flowmaster Outlaw series Axle-Back Exhaust add horse power to your Mustang.

2Mac Year: 2007 Model: GT

  • That is a big yes and they sound real good and meaty.

    Best Answer

    Noeffort Year: 2010 Model: GT

    Good Answer (1)

Show 2 more answers Question Resolved

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Customer Reviews (100+) Write a Review

Overall Rating 4.9

out of 5 stars

Installation Time:Afternoon

Installation Cost:0-$100

  • Loudness / Volume 4.862069 4.9
  • Exhaust Note 4.896552 4.9
  • Fit & Finish 4.62069 4.6
  • Bang For Your Buck 4.791907 4.8

  • 5/5

    Installation Time: Afternoon

    June 18, 2013

    You will love them...your neighbors won't!

    I am not big on writing reviews but after installing these, I felt AM and Flowmaster deserved a review. First off, thanks AM for getting these to me in less than 24 hours, can't ask for much more than that. Secondly, I am a very amateur wrencher, I've done the majority of the work on my car minus my cam installation, and these went in perfectly. Removing the old hangers is a different story. Removing rusted in bolts, located where only a 9 year old girls hands could reach was a pain, so it took me a little longer than the typical hour long install noted by other reviewers. My suggestion is putting penetrating oil on the (8) bolts the night before, and using anti-seize during the re-install. Now to the good part, I have basic bolt-ons including Steeda cold-air kit, Comp Stage II VSR cams, Kooks long tube headers, and a custom tune. Previously I had Flowmaster American Thunders mounted which I loved but after watching a few re-runs of Monster Garage and hearing the phrase "if you can't hear it before you see it" kicked around, I decided to get something a bit less dainty. Let me tell you, these make my GT sound like an absolute terror coming down the street. Some days I will go out and cruise around in 2nd gear and will be giggling like a little girl the entire way. It is definitely an acquired sound, differing from the AT Flows with their low and lopey sound. These sound more like a semi-truck rolling down the thruway. Like many other reviewers, it does have a decent amount of drone; I'm geared at 4.10's so I get it around 1800-2200rpm. It can be a little annoying but it is easily remedied by giving it a little more gas. And WOT is simply devastating. If you enjoy driving down a city street and setting off every car alarm along the way, or getting the finger by the Audi driver next to you who can't hear his blu-tooth phone call, then the Outlaws are for you.


    Year: 2005 Model: GT Driving Style: Street / Strip 'Stangs I have owned: 1 Buffalo, NY, USA

    Helpful (30) (1)

  • 5/5

    Installation Time: Afternoon

    November 03, 2012

    So much better than....

    I installed the Pype Bombs first and had a rough time with the fit. These are so much better fit and finish, these were easy to align and center in the cutouts and the sound is amazing!!! I think the tone is deeper than the Pypes and don't sound so steel canish. In my opinion spend the extra money and go with Flow Master first.


    Year: 2006 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 5+ Mississippi

    Helpful (11) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    October 18, 2013

    No Two Flowmasters Are The Same

    I was running a set of 60-Series Flowmaster axle backs on my 2008 Bullitt for the last year or so. They sounded ok driving around town, but I never liked how tin-canny they sound when you open it up. Still, I tolerated them. But something happened a week ago that sent me looking for a better-sounding exhaust. I was driving with my girlfriend in her car when a Subaru WRX with one of those silly potato cannon exhausts rolled up alongside us. My girlfriend looked over at me and said, "Hey, that sounds just like your car." I was so horrified that I began researching for a new set of axle backs immediately after returning from dinner. After hours of research and sound clips, I was torn between the Pypes Pype Bombs and the Flowmaster Outlaws. I decided to go with the Outlaws based solely on the customer feedback. I crossed my fingers and placed the order. In the back of my mind, I was very concerned that the distinct Flowmaster tin-can sound would still be there in these Outlaws. I was also concerned that the Outlaws wouldn't be much different from the 60-Series set I already had. I was worried that I had made the wrong decision. Let me tell you in no uncertain terms that I am 100% happy with my decision now! The sound of my Bullitt can no longer be compared to a Subaru with a potato cannon! As a previous reviewer said, they don't call these things "outlaws" for nothing. I would estimate that they are at least 40% louder than the 60-Series. They have a very deep, sinister rumble at the lower RPM's, and when you step on the gas they just absolutely ROAR. My daughter was driving behind me last night and she said the inside of her car was vibrating when I would take off from a red light, and I wasn't even putting the hammer down. These axle backs sound so amazing that I have to wonder why Flowmaster would manufacture pipes that are anything less than these Outlaws, and I wonder why any Mustang owner wouldn't want their pony to sound exactly like this. You don't like loud? Then what are you doing in a Mustang? The only bad thing I can say about the Outlaws is that they do not bolt on perfectly with the tips centered in the exhaust cutouts. Yes, they can be adjusted, but Flowmaster should've just manufactured these for the 2005-2009 Mustangs and left out the 2010, which would probably solve that issue. I had them installed by a local shop. I'm not sure where to rate these on the obnoxious scale because it really depends on what kind of neighbor you are. If you want your neighbors to hate you, you can certainly accomplish that with the Outlaws. Run down the street in 1st or 2nd gear and you are sure to scare people out of their underwear. They may tolerate you if you take it easy, but they will still hear you coming or going. If they can't appreciate that American muscle sound, maybe they're not worth the consideration anyway ;) In closing, I highly recommend the Outlaws to any Mustang owner who wants their pony to sound like a lion roaring on the Serengeti Plain. I promise you won't be disappointed.


    Year: 2008 Model: Bullitt Driving Style: Show 'Stangs I have owned: 3 Lansdale, PA, USA

    Helpful (8) (0)

  • 5/5

    Installation Time: Afternoon

    May 17, 2014

    What will you decide?

    Before purchasing these, you have to ask yourself a question: Do I want to continue to live a mundane, 9-5, stock exhaust life? Or do I want to frighten small children, have women flock to me in droves, and send Camaro owners home crying to their mommies? If you choose the latter, these pipes are for you. Mean and nasty, they sound incredible when driving downtown between buildings. They do drone, so be prepared for that. But it is a small price to pay for the new found prestige,respect and glory that will be coming your way. I had mine installed by by the muffler shop so not sure on the install time for these. Technician pulled them out of the box and said, "Oh man, it's THESE!" After they were installed, all the guys in the next door transmission shop came out to see what the ruckus was all about.


    Year: 2007 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 1

    Helpful (7) (0)

  • 5/5

    October 16, 2011

    Flowmasters Finest

    Bought these before American Muscle even had them and they are truly unbelievable. I have them on with a bassani x pipe, headers, steeda CAI, and couple other bolt ons and these things scream. Flowmasters loudest product by far. They DO NOT quiet down after 3k rpms like most chambered flowmasters, they get louder. These and slp's are evenly matched in loudness surprisingly but these are better because its flowmaster. Definitely not for daily driving.


    Year: 2005 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2 Staten Island. NY

    Helpful (7) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    August 28, 2012

    Absolutely Amazing!!

    if you want your mustang to have a "ballsy' aggressive sound this is definitely the exhaust to have! Flowmasters are the best out there and this exhaust proved that. easy install and had it growling in no time. Great product!!!!


    Year: 2005 Model: Cobra Driving Style: Daily Driver 'Stangs I have owned: 2

    Helpful (7) (1)

  • 5/5

    Installation Time: Less than 1 Hour

    September 27, 2012

    Amazing product! Very aggressive sound.

    VERY loud and VERY awesome!! aggressive through and through. i have received no negative feedback and all compliments. my gf even loves them!! definitely recommend this to anyone!!!


    Year: 2006 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2 Aransas Pass, TX, USA

    Helpful (5) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    July 08, 2012

    Amazing difference

    These pipes are EPIC! I just bought my '08 GT/CS about a month and a half ago and the only real "problem" I had with it was that it was WAYYY too quiet. After reading reviews and checking ratings, I decided on this axle-back system and I can easily say I do NOT regret that decision. These pipes are LOUD, they turn heads, they demand attention and having done nothing else to the car (yet), it already has the loud aggressive sound I wanted for it. I highly recommend them to anyone. Install time was roughly an hour maybe hour and a half on the lift in our garage. The hardest part is taking off the stock mufflers, I still have the scratches to prove that one!


    Year: 2008 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 2 Annapolis, MD

    Helpful (5) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    January 03, 2013

    Angry exhaust

    Mufflers are real aggressive. They definitely get you noticed. Snaps a neck almost every time. Great sound. Better in person as compared to sound clip.

    Top 500 Contributor


    Year: 2007 Model: GT500 Driving Style: Daily Driver 'Stangs I have owned: 5+ Sayville, NY, USA

    Helpful (5) (1)

  • 5/5

    Installation Time: Afternoon

    November 15, 2012

    Very aggressive sounding!!

    This is an awesome sounding exhaust. I installed it on an '09 GT500. The only issues with installation is removing the stock exhaust. You either have to cut the stock hangers or remove the hanger brackets. Installing and alinging them was really easy. If you like to get attention from bystanders, you'll get noticed with these. At 2000RPM's I'm getting a significant amount of drone inside the car tho, hoping this will lessen when they are good and broke in (for better terms). Completely recommend tho!! This is NOT your typical Flowmaster's, They are BETTER!


    Year: 2009 Model: GT500 Driving Style: Daily Driver 'Stangs I have owned: 5+ Fort Rucker, AL, USA

    Helpful (5) (1)

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