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Flowmaster American Thunder Axle-Back Exhaust (05-09 V6)

100+ Reviews
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  • Item #18404
  • MPN# 17421

  • Market Price $281.34
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  • Aggressive Flowmaster 60-Series Delta Flow Sound
  • Polished Stainless Steel 3.5" Tip.
  • Durable Aluminized Steel Construction.
  • Includes One Flowmaster Muffler
  • Fits 2005-2009 V6 Mustangs.

Flowmaster Sound . The Flowmaster American Thunder Axle-Back exhaust system will improve your 2005-2009 V6 Mustangs exhaust flow for an increase in power and a throatier muscular exhaust note with their patented chambered designed muffler.

Quality Construction. Constructed from durable 2.5" 16 gauge aluminized steel tubing for it's corrosion resistant properties the Flowmaster axle back features a specialty 5" X 10" chambered 60 Series Delta Flow American Thunder muffler with a 3.5" diameter polished stainless steel tip for muscle car looks and sound. As an added bonus the tip is embossed with the "Flowmaster" logo for true custom styling.

Fitment. This Flowmaster American Thunder Axle-Back exhaust system is designed to fit the 2005-2009 4.0L V6 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 Details

What's in the Box
  • (1) Muffler assembly
  • (1) Exhaust Hanger
Installation Info
Tech Specs
Axle-Back Exhaust Specifications
Piping Material: Aluminized Steel Tip Material : Polished Stainless Steel
Piping Size: 2.5" Tip Size: 3.5"
Muffler Type: Chambered Fitment: 05-09 V6 Mustangs
Will it fit my Mustang?
  • V6 - 05, 06, 07, 08, 09

Most Helpful Reviews


When ordering the Flowmaster I did a lot of reviews and all my research. So I purchased the Flowmaster and it arrived about a week later. After putting my exhaust on (easy installation) and finally hitting ...

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Helpful (1)


Install took about 1hr & I didn't even have to jack up the car. The muffler slid right in & the bolt up was a snap. I noticed an increase in highway gas mileage by about 1.5 mpg. The sound is great ...

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Helpful (5)

Overall Rating 4.8 out of 5 stars
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9 Questions / 16 Answers

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My alignment is do i fix it? I just installed this axelback with my father & i just love the way it sounds & looks but unfortunately the tip isn't aligned with the cut's more to the left of the cut out. I really want it to be aligned in the center, any advice would be greatly appreciated! Thank you AM!


  • This exhaust naturally tends to linger to the left more then the right. but not by much, MAYBE 2cm or less in my case. but if it is a lot more significantly to the left in your case, i would recommend loosening the hangars and maybe even where it connects to your underline exhaust, and have one of you hold it to the right as much as possible to the point where your satisfied with the position, and while holding it in that exact position, have either you or your father tighten every thing back up and see where it goes from there. hope this helps, Goodluck!


    Good Answer (5) (0)

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It fits 2010 V6?


  • Unfortunately this axle-back is not meant for the 2010 V6, but there is a version of this designed specifically for the '10. Check out the link below.


    Good Answer (0) (0)

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Does this improve gas mileage? I have a 2008 V6 auto. So far I only installed the replacement air filter. If I add this muffler and the cold box air filter, will they increase my gas mileage? I don't really care about increased exhaust noise.......Thanks


  • It may, ever so slightly, increase your mileage because you are allowing your exhaust to flow easier. Although you are helping your pony breathe, it shouldn't be enough to make a huge difference.


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would the check engine light come on installing this? i know this is a dumb question but i just was wondering after installing this would i need to tune the car at all or would it cause the check engine light come on if i put this on?


  • No... Mine Worked Fine...


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Around how much horsepower does this add?


  • As others have said, it's generally around a 6-10 hp gain. This amount of gain tends to be hard to actually feel but it is there! Hope this helps!


    Good Answer (8) (0)

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How well will this worth when i install long tube headers?


  • The Flowmaster American Thunder Axle-Back Exhaust (05-09 V6) will work amazing with a set of long tube headers. Long tube header's are more free flowing than your restrictive stock shorty headers. You'll see a nice gain in performance as well as sound. Along with these Axle-Backs, your Mustang is going to sound 10x more aggressive whiling having a nice power gain.


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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 4.52 4.5
  • Exhaust Note 4.626437 4.6
  • Fit & Finish 4.737143 4.7
  • Bang For Your Buck 4.697143 4.7

  • 5/5

    July 24, 2016


    When ordering the Flowmaster I did a lot of reviews and all my research. So I purchased the Flowmaster and it arrived about a week later. After putting my exhaust on (easy installation) and finally hitting the gas for the first time I couldn't believe the sound quality. What a MONSTER of an exhaust. Way better than I thought it was going to be I'm so happy I made this purchase! Totally recommend it !


    Year: 2007 Submodel: V6

    Helpful (1) (0)

  • 4/5

    Installation Time: Afternoon

    October 21, 2013

    Good Upgrade If You Can't Afford True Dual Exhaust

    Pros: Definitely sounds stronger when starting and accelerating. No annoying sound inside at any speed. Fit was perfect on '07 V6 - you don't need the extra hangers. Cons: (if I have to find some) Fairly quiet at idle. Takes longer than the 1/2 hour mentioned because you can only get about 1/4 turn on most bolts....still just a little over an hour total.


    Year: 2007 Submodel: V6

    Helpful (1) (0)

  • 4/5

    Installation Time: Afternoon

    July 15, 2012

    Great sound, some minor product issues

    So this was my first install of anything on a car. The inlet pipe of the flowmaster had one side bent nearly flat. It was so flat that I thought this was how the end of the exhaust was going to look (it looked like an intentional molding). Once I got the stock muffler off, though, it was apparent this was not how the end should look. After visiting an auto parts store and finding a tool, I was able to flange the inlet open to get it on. Once that was done, install was pretty quick (less than 30 minutes). Next, I experienced rattle at certain rpm's while driving. I checked all the clamps and hangers, all was tight. I thought at first maybe it was because the stock V6 muffler included a dampener, and the flowmaster did not. Nope. Turns out it was the connection at the inlet pipe. Even though the supplied clamp was tightened to the point of stripping, it was not providing any real stability, so I added an extra "hanger" via a rubber ring and a hose clamp, and it fixed it immediately. I suspect it's possible that the initial bend of the inlet also affected the fit and the clamping. I don't know if it got dropped during shipping or what. Had this been a ready to put on piece, my overall rating would have been 5 stars. As to the muffler, it sounds great. It's quiet at idle and cruising speed, yet gives a nice amount of noise when accelerating.


    Year: 2007 Submodel: V6 Raleigh, NC, USA

    Helpful (2) (0)

  • 5/5

    May 31, 2011


    Install took about 1hr & I didn't even have to jack up the car. The muffler slid right in & the bolt up was a snap. I noticed an increase in highway gas mileage by about 1.5 mpg. The sound is great & its a major improvement from the stock muffler. (I'll take a Flowmaster over any other muffler anyday)

    Jeremy Truelove

    Year: 2006 Submodel: V6

    Helpful (5) (0)

  • 5/5

    August 19, 2010


    The muffler is exactly what I wanted, it's slightly louder than stock at idle and cruise but when you come off a red-light it roars!!!! Defintely not a V8 sound but 1000% better than stock


    Helpful (4) (0)

  • 5/5

    November 17, 2009


    I love the sound of this muffler. mine doesnt sound as ricey as the one in the video though. sounds beastly for a v6. My dad says it sounds better then his v8s stock. i got the BBK CAI and it makes it sound cleaner i think.


    Helpful (5) (0)

  • 5/5

    July 06, 2010

    Ohhhh Baby...

    My word... Got my car, a lovely 09 Mustang, and immediately started looking for a new muffler. Why? Because, the stock muffler STINKS! After a TON of research, I decided on this one. BEST CHOICE EVER! My parents actually bought it and my uncle installed it while I was on a trip. Came home late, cranked up my car, and paused... "Was that..." Looked around back and there was that pretty "flowmaster" chrome tip. It sounds amazing, and trust me, no video does it justice. It has a nice, deep sound. Doesn't "pop" much. Only does it when I start it, and even then only every so often. Muffler is definitely the first V6 mod you should do, and in my opinion, this one is by far the greatest!


    Year: 2009 Submodel: V6

    Helpful (25) (0)

  • 5/5

    July 04, 2010

    It Sounds Awesome!

    i bought this flowmaster and it arrived in just 3 days. i had it professionally installed and it sounds amazing! it makes your v6 sound soo much better. Next year i plan on getting a true dual with both of these flowmasters on my mustang. i recommend buying this exhaust to get rid of the whiney sound of the stock muffler!


    Helpful (25) (2)

  • 5/5

    March 08, 2010


    Just got it today and installed it right away. it took me two days to pick the right exhaust that would give my v6 what it needed to sound the way it looks. Let me tell you this exhaust sounds great. The flowmaster give the mustang a deep rich sound when u hit the gas. Like another reviewer said i stop listening to the radio just so i can hear it. One bad thing ,well its not that bad but everyone on the road wants to race since i put it on. That is how good it sound. dont take my word go to youtube so you can hear it for yourself. Highly recommended.


    Helpful (13) (0)

  • 5/5

    September 08, 2009


    hey mustang lovers, after looking for weeks for an affordable exhaust system for my v6 stang, i found this. after reading some of the reviews i was skeptical. But i went out on a limb and i am so happy! i had it installed at 9 am this morning and i LOVE it. it sounds amazing when u turn it on and at idle. Acceleration- loud when u want it and soft when u dont. sorry about all the grammar mistakes on my review, im just so excited!!!! buy this product


    Helpful (13) (1)

  • 5/5

    June 16, 2010

    Great Exhaust

    I was a little leary about buying this exhaust. I shouldn't have been. I installed it with every intention of putting the OEM back on if I didn't like it. I won't be taking it off. It gives my 09 Convertible V6 a nice rumble at idle, and you can really hear it during a quick acceleration. Once you reach your cruising speed its nice and quiet. Its not obnoxiously loud at all. I could feel the HP difference immediately. I have nothing bad to say about it and American Muscle delivered it quick. A BBK CAI is next. I hope this helps if your riding the fence.


    Year: 2009 Submodel: V6

    Helpful (30) (10)

  • 5/5

    Installation Time: Less than 1 Hour

    September 20, 2011


    sounds amazing, good increase in HP, and looks great!! had it installed at a shop for $40 bucks and it only took them 30 min!!!


    Year: 2007 Submodel: V6 san antonio

    Helpful (10) (1)

  • 5/5

    December 03, 2010

    A wonderful product at a great price

    As a mustang V6 owner (2007) the first thing I wanted to do was get some bolt-ons. I looked at cold air intakes, exhausts, and chips. The first thing I decided to do was this flowmaster exhaust. I am very glad I did. The bolt on horsepower is noticable and the car sounds amazing. at idle the car sounds louder then stock with a deep growl. At about 2500 rpm the note gets really loud and deep sounding identicle to my friends v8 truck with an exhaust. this product will make your stang a lot funner to drive as well as turn some heads. I would buy this again as the first stang upgrade in a heartbeat


    Year: 2007 Submodel: V6

    Helpful (8) (0)

  • 5/5

    April 23, 2010


    I do all my mods to my car. This took me about an hour to install with the no power tools. I didn't get the extra $60 hangers and it is tightly in place in an 09 V6. Sound is so buff. I posted a video on YouTube if you doubt its buffness. Throttle response if ridiculously improved. I spent my Tax Refund well. :)


    Year: 2009 Submodel: V6

    Helpful (8) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    September 09, 2011

    Easy installation, great fit, and amazing sound!

    Highly satisfied! First mod done to my stang, easily installed in about 45 minutes, amazing sound especially in higher rpm's, and boost in power. I get alot more challenges to race ever since I got the exhaust and I'm happy to say my stock 210 hp v6 pony with Flowmaster exhaust took out an Infiniti G37 S. I highly recommend this product!


    Year: 2005 Submodel: V6 Los Angeles, CA

    Helpful (7) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    September 22, 2011

    This product has Excellent qualities!!!

    When i first installed it, just from the looks of it i knew that i qould like it. When you first crank the engine and it starts up man are you SURPRISED at what it actually sounds like. Everyone has heard a lions roar, well thats exactly what you get when you start it up. Idleing like at a stop light you dont hear it at all. But once you hit the gas even just the slightest you can hear and feel the growl throughout the car. All in all this is the best and first thing someone should buy for their Mustang.


    Year: 2009 Submodel: V6 Oklahoma City

    Helpful (8) (1)

  • 5/5

    February 27, 2011

    I love this exhaust

    I love this exhaust. It was delivered quickly. I had it put on and it sounds great. The difference was instantly noticeable. The sound of the exhaust when I press the accelerator is so much better now. If you have a V6, this is a must have.


    Year: 2007 Submodel: V6

    Helpful (5) (0)

  • 5/5

    March 07, 2010


    I was so nervous to purchase a new exhaust for my 2010 Mustang. I wanted to make sure it was going to have the sound I was looking for. I wanted my Mustang to have a rich deep growl to it...and let me tell you, this Flowmaster did NOT disappoint me at all. I took it down to my mechanic and he installed it within 15 or 20 minutes. I would highly recommend this product to any V6 Mustang owner out there. The sound is amazing. If you have any hesitations about this product you need not worry. You're going to love it. I used to be the type that would have to listen to the radio or a cd while driving but I haven't done any of that since I had this installed. I'm too busy listening to my Mustang GROWL!!!

    Jeanette G.

    Year: 2010 Submodel: V6

    Helpful (5) (0)

  • 5/5

    August 20, 2010

    A must have...

    I wanted a strong sounding, gurgly exhaust sound. I took off the stock exhaust and drove around with out a muffler for a bit for kicks. I loved that sound, but it was a bit loud. After putting on the flowmaster, i was suprised that the exhaust sounded even better, and the volume was still at a level where people will turn their heads when you pin it. When you lift off, the drone disappears. Sounds awesome on cruise control. Easy to install, only complaint is that the muffler gets VERY hot, and you can smell hot plastic, almost as if the bumper is about to melt, so dont get the tip too close to the bumper.

    Chris Al.

    Helpful (6) (1)

  • 5/5

    April 18, 2010


    This is a must for any V6 Mustang. It definitely gives the car a headturning sound. I've been getting compliments on the car from total strangers ever since I put it on.


    Helpful (6) (1)

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