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SLP Loudmouth Axle-Back Exhaust (11-14 GT; 11-12 GT500)

Item 23042
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      Review & Installation Video

      Hey what’s up everyone I’m Justin from, and I’m bringing you SLP’s loudmouth axle-back exhaust, for your 2011 and up GT Mustang. This loudmouth system eliminates the restrictive factory mufflers, which allows for more horsepower, it also makes for one mean exhaust note as well. The system is constructed from 3 inch mandrel bent stainless steel tubing, exiting through hand polished 4 inch tips, which result in a very clean finish. Simple bolt on installation, should only take you about an hour. Let’s hear how SLP’s loudmouth axle-back compares to your factory exhaust.

      Product Information

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


      • Rich, Throaty Exhaust Sound
      • Muffler Delete
      • 2.5" Mandrel-Bent 409 Stainless Steel Tubing
      • 4" Polished 304 Stainless Steel Tips
      • Emissions Legal in All 50 States
      • Fits 2011-2014 GT and GT500 Mustangs


      Aggressive Throaty Exhaust Note. This SLP Performance Parts Axle-Back kit eliminates the restrictive stock mufflers from the 2011-2014 GT or GT500, drastically reducing back pressure to enhance power and to produce one of the most aggressive exhaust notes possible with the factory catalytic converters still installed. 409 Stainless Steel. SLP's Loud Mouth axle-back system is made from 2.5" mandrel-bent 409 stainless steel tubing, which has excellent flow characteristics and features pre-welded hangers for simple installation. The hand polished, 4" dual wall tips give a show quality muscle car appearance to the rear of your Pony. Application. Made as a direct bolt on, this SLP Loudmouth Axle-Back bolts right up in the stock location without any modifications required on the 2011-2014 GT or GT500 Mustangs.

      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: 2011 2012 2013 2014 Details

      MPN# M31023

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (94)

      Write a Review

      Ratings Summary

      4.7 out of 5 overall rating from 94 customers

      Installation Time: Afternoon

      Installation Cost: 0-$100

      • January 10, 2020

        5 2013 GT - Ktorr04 Installation Time: Less than 1 Hour

        Exactly what I wanted !

        Sounds exactly how I wanted it to ! Worth every dollar ! Nice tone, especially when youre accelerating !

        Helpful (0)
      • October 17, 2019

        5 2012 GT500 - Phijar

        Mean sound! Easy install

        I swapped the stock GT500 mufflers for the SLP loudmouth. Install was easy and fitment is good. These are significantly louder than the stock muffler - I like it! Transformed the sound of my GT500.

        Helpful (0)
      • December 31, 2018

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


        Perfect fit, and looks awesome!! I love the SLP tips!

        Helpful (1)
      • November 25, 2018

        5 2014 GT - HugoB Installation Time: Less than 1 Hour


        These SLP Loudmouth axle backs are amazing. As soon as I installed them you could hear a HUGE differenc. Loud cold start sound as well as a nice low rumble at idle but once you floor it you will be heard miles away! These SLPs let the 5.0 roar with a great sound.

        Helpful (1)
      • July 20, 2018

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


        Just installed mine this morning. It took no more than 20 minutes (installed with lift). Has a badass sound. Few months ago I removed the OEM exhaust and went to a muffler shop and had a straight pipe installed but you can’t compare the SLP. I highly recommend! Won’t be disappointed!

        Helpful (2)
      • July 04, 2018

        5 2013 GT - Whawkins Installation Time: Less than 1 Hour

        Insanely loud

        This exhaust makes me drive around with my windows down in July in Texas. Because hearing the car is worth the heat. Insanely loud. Definitely not for those trying to keep a low profile. Hope you're good at shifting if you have the 6 speed, because everyone's going to hear every detail of your shift. Goes from loud to just plain rude right around 3,000RPM.

        Helpful (4)
      • July 04, 2018

        4 2014 GT - MarkK Installation Time: Less than 1 Hour


        Little louder than expected Drone inside at 2000 rpm or when under slight load at lower rpms. Simple to install. Didn’t need extra mounts that were recommended. Waste of money there. Overall good

        Helpful (2)
      • June 29, 2018

        5 2014 GT - RicardoP Installation Time: Less than 1 Hour


        Best best exhaust I’ve ever bought worth every dollar!

        Helpful (2)
      • June 03, 2018

        5 2011 GT500 - RJTINStang

        Let it rip!

        Wow!! One of the best mod I've had so far on my 2011 Shelby GT500 . I definitely recommend this product. Thank you AM.

        Helpful (2)
      • May 13, 2018

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


        Awesome exhaust. But if you see any cops be careful, I always hold the clutch in just in case passing by them. Overall it makes the mustang sound like a beast!

        Helpful (4)

      Questions & Answers (14 answers)

      5 Top Rated Questions

      are these louder than the flowmaster outlaws and would they sound better with a resonator delete or cat delete

      • Unfortunately this exhaust will not be louder than the Flowmaster Outlaws. In regards to going with a resonator delete or cat delete. I would recommend the resonator delete. This will provide a good sound boost, but will not be obnoxious like if you deleted the cats.

      Helpful (4)

      Which X-Pipes would work with the slp loud mouth axle backs to make the car louder ?

      • No x-pipe is really louder than another. Volume-wise, the difference will be negligible.

      Helpful (0)

      Will this work with the LTH Over Axle Pipes (11-14 GT, GT500)?

      • The LTH over axle pipes have a diameter of 2.75" whereas the SLP Loudmouth axleback exhaust has a 3" pipe diameter. For these to work together you will need a 2.75" to 3" step up pipe modified for proper installation.

      Helpful (0)

      Debating on these or flowmaster outlaw for my GT500 is their any back pressure in these or the flowmaster outlaws??

      • There will not be any back pressure with these SLP Loudmouth's or with the Flowmaster Outlaws if they have been installed correctly.

      Helpful (0)

      I have these and they drone way too much around 1.7k-3k, I heard I can buy a mid pipe and fix this issue. Can you guys recommend one for this problem

      • Hello! We have many different options to take when looking at mid pipes, I would recommend that you look at one that is catted, if you are looking to quiet down the drone a little bit!

      Helpful (0)
      Post Your Question
      9 More Questions
      I'm stuck between getting the SLP or Flowmaster Outlaws. I want the one that has a real good tone to it and sounds like thunder clapping. is muffler deletion better? I'm leaning more towards the SLP but I need some help. 1 answer
      Are the tips interchangeable. I want black tips and other than having them powder coated can these be changed out with black tips or no? 1 answer
      I got a 14 shelby and ordered the loudmouths, do I have to have the exhaust hanger kit or is it optional? 1 answer
      are the slp loudmouths alot louder than the borla ataks? i want a really loud exhaust but also want it to not sound so raspy... I wanted to know if the borla ataks are a lot quieter because I like the sound of them 2 answers
      compatibility I have the Magna flow cat back competition series, will this be a straight axel back swap without cutting, will this help or hurt performance, and will it be deeper or higher pitched? 1 answer
      Will this be LOUDER and/or DEEPER than the Outlaw Axleback I currently have the Outlaw Axleback installed on my 2011 5.0 with a resonator delete. Will switching to the SLP make it MUCH louder? and will it be deeper? because the Outlaws are loud, but not loud enough for me. and I really want a louder exhaust and can't decide on which one to get. So please help me out! thanks 3 answers
      How much horsepower will this exhaust add? 2 answers
      Will this kit and/or the Rousch axle backfit the 2012 Club America Edition? Comes epuiped with dual factory mufflers. Have the 2012 Mustang Club or America edition. It is a V-6 and want remove the dual factory mufflers and replace with either the SLP Loudmaouth or Rousch axle back exhaust systems. 1 answer
      will this exhaust sound better with 1-3/4" SLP long tube headers? I am for sure wanting to buy the SLP Loudmouth Axle-Back, but i would like to give it an even rawer mustang sound. i was wondering if that would work or if there was something a little less expensive that would accommodate for the same thing. 2 answers

      Installation & What's in the Box

      Installation Info

      What's in the Box

      Hardware included:Hardware Included
      • (2) Clamps

      Tech Specs

      Axle-Back Exhaust Specifications
      Piping Material:409 Stainless Steel Tip Material :Polished 304 Stainless Steel
      Piping Size:2.5"Tip Size:4"
      Muffler Type:NoneFitment:2011-2014 GT and GT500 Mustangs

      Will It Fit My Mustang

      • Boss 302 - 12, 13
      • GT - 11, 12, 13, 14
      • GT500 - 11, 12, 13, 14

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