Free Shipping On Orders Over $49. Details

Talk to a Mustang Expert
1-877-887-1105
Every day 8:30AM EST - 11:00PM EST
Win Any Wheel & Tire Package! Enter Daily

SLP Loudmouth II Axle-back Exhaust (15-17 GT Fastback)

Market Price $467.99 You Save 4% ($18.04)
Our Price

$449.95 (pair)

FREE Shipping

  • Item 387059
  • MPN# 620055

Will this fit your Vehicle?

In Stock Ships same business day.
Ship to: Ashburn - 20149
Sorry, please enter a valid US or CA postal code
We're sorry, zip can't be updated at this time.
    Create a list
    Add to New List

    Saved - View your saved items

    We're sorry. We couldn't save this product at this time.

    Features, Video & Details

    • Sporty Muscle Car Sound
    • Durable 409 Stainless Steel Construction
    • 2.5" Mandrel-Bent Tubing
    • 4" Polished 304 Stainless Steel Tips
    • Cut & Clamp Installation
    • Emissions Legal in All 50 States
    • Fits 2015-2017 GT Fastback Mustangs

    Review & Installation Video

    Review & Install Video

    Hey, guys, Stephanie with AmericanMuscle.com here with my review of the SLP Loudmouth II Axle-back Exhaust for 2015 to '16 Fastback GTs. My first impression of this axle-back is that it offers a deeper, more reserved muscle car sound. Around 2,000 to 4,000 rpm, the system does get louder, and it increases in sound as you get into those higher rpms, but it maintains the deepness and throaty quality. It doesn't get raspy at all. Even from inside the car, the axle-back sounds deep and has no drone, which is perfect for a nice cruise or good sound quality from light to light in town. And, luckily, the sound can be there when you want it to be, you've just got to step on it a little bit harder. Keep in mind that this is an axle-back, so you'll be keeping all of your cats and your stock resonator. Now, down the road, you can always change out your resonator for another mid-pipe option and enhance the sound of the axle-back even more, and that's one of the nice things about an axle-back. It offers room to grow and change for different things like mid-pipes, off-road setups, or headers. I'm going to rate it as a two on the loudness scale because while it is deep, it's not the loudest thing out there on the axle-back market. If you're looking for loud from an axle-back, there are other systems out there that are sure to give you what you're looking for. In fact, SLP does have a muffler delete option for you guys out there that are looking for loud. So, we're looking at 2 ½" manual-bent stainless steel tubing with 4" polished stainless steel tips, rocking the SLP name here, and a pair of straight-through mufflers at one of the most budget-friendly prices that we're seeing out there on the market for the S550 GT and from a brand that's known for their exhaust products. I'd say that this is a good deal here if you're looking for a louder but more tame muscle car sound from an axle-back. Install-wise, if you don't know by now, if you're installing an axle-back, you're going to be doing some cutting, and this axle-back is no different. It's a standard cut-and-clamp design that we're used to seeing with other axle-backs, and for that reason, I'm going to stick with what I said in the past and call this a two out of three wrenches on the scale. Time-wise, it's not really going to take too long to install, probably about an hour or so, but you do have to be careful when you're cutting. And remember that this system is not compatible with convertibles. I still just recommend a fresh sawzall blade and some eye protection, just to make sure everything goes smoothly. Wrapping this up, the SLP is one of the inexpensive options on the axle-back scale when we compare it to the rest of the market, and if you're looking for a deep and throaty but more civilized exhaust tone, then this would be a good option for you. The straight-through mufflers are going to wake your 'Stang up some and provide you with a little extra sound and the option to further change your exhaust down the road. As always, feel free to check out the full line-up of axle-back options, here at AmericanMuscle.com.

    Sporty Muscle Car Sound. Give your Coyote powered S550 Fastback Mustang a sporty muscle car tone with only minimal harshness by installing a SLP Loudmouth II axle-back exhaust system from AmericanMuscle. The Loudmouth II not only enhances the sound of your late model Mustang, but it also enhances performance by drastically reducing back pressure for an increase in horsepower and torque.

    Stainless Steel Construction. Manufactured from 2.5" diameter mandrel-bent stainless steel tubing for its excellent flow characteristics, this SLP Loud Mouth II exhaust system features a pair of straight-through performance mufflers that end with highly polished 4" dual wall exhaust tips for intimidating muscle car looks and sound.

    Cut & Clamp Installation. The installation of this Axle-Back Exhaust requires cutting and removing the factory muffler assemblies, and clamping the new muffler assemblies in place. Clamps and instructions are provided.

    Application. This SLP Loudmouth II Axle-Back Exhaust system is specifically designed to fit 2015-2017 GT Fastback Mustangs only. Cutting of factory exhaust is required for installation. Not compatible with convertibles.

    Fitment: 2015 2016 2017 Details

    CA Residents: Warning: California's Proposition 65

    What's in the Box
    • (2) Axle-Back Assemblies
    • (2) Polished Tips
    • (4) Clamps
    Installation Info
    Tech Specs
    Piping Material: Stainless Steel Tip Material : Polished 304 Stainless Steel
    Piping Size: 2.5" Tip Size: 4"
    Muffler Type: Straight-through Fitment: 2015-2017 GT Fastback
    Will it fit my Mustang?

    You Might Also Like

    Customer Photos (15) Submit Your Photo

    View All 15 Photos

    Questions & Answers (3)

    3 Top Rated Questions

    Video says this system is not compatible with convertibles. Why is that? I have looked at most of your axle back videos on this site and this looks very similar to Roush, which fits verts. So why not this system????

    • The SLP Loudmouth II Axle-back Exhaust is only designed to work with convertibles because of the design of the pipes and flanges. They will not bolt up correctly to a convertible.

    Helpful (1)

    After the install,will I have the check engine light come on? Sense there's change in torque and back pressure.(2016 gt).thank you.

    • With the install of the SLP Loudmouth II Axle-back Exhaust - Fastback (15-17 GT) you will not get a check engine light. These will install with no issues.

    Helpful (1)

    These mufflers would sound a lot like the original Borla Stingers right? Since they are both straight through design?

    • This axle backwill sound a bit alike but the Borla stingers but the stingers will be throatier than the SLP. 

    Helpful (0)
    Post Your Question

    People Who Bought This Item Also Bought

    Customer Reviews (32) Write a Review

    Overall Rating 4.9

    out of 5 stars

    Installation Time:Afternoon

    Installation Cost:0-$100

    • Loudness / Volume 3.677419 3.7
    • Exhaust Note 4.967742 5.0
    • Fit & Finish 4.870968 4.9
    • Bang For Your Buck 4.903226 4.9



    • 5/5

      Installation Time: Afternoon

      July 15, 2018

      SLP loudmouth exhaust

      has a great sound much better than the stock exhaust but not too loud.

      GarhardM

      Year: 2017 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      July 14, 2018

      Slp!!

      I installed this together with a heartthrob h pipe and it sounds really clean I get a lot of compliments about how clean it sounds and that its the way the 5.0 should sound overall happy with this system I would recommend it to anyone

      8cyl302

      Year: 2017 Submodel: GT

      Helpful (4)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: 0-$100

      May 12, 2018

      WOW, just what I wanted!

      DEEP! Good sound, louder than the original, but not overly. I missed my 2016 Scat Pack Challenger's sound so much, well, not any more, this is very good, great quality!

      paul1966

      Year: 2015 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      May 01, 2018

      Roush was to raspy for me

      Paired this with my h pipe. Sounds amazing. My Roush was to raspy for me and this is deep all the way through the rpms. If the Roush was a 10 for volume, id say this setup is an 8. You need the h pipe or x pipe to enjoy the sound of this axle back, in my opinion.

      Lufty

      Year: 2017 Submodel: GT

      Helpful (8)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: 0-$100

      February 16, 2018

      slp loudmouth II

      sounds really good on the 2017 gt. not too quiet and not too loud. they are just right in my opinion

      bo308

      Year: 2017 Submodel: GT

      Helpful (7)

    • 5/5

      Installation Time: Afternoon

      February 15, 2018

      SLP Loudmouth II Axle-back Exhaust

      Nice finish and easy to install. Love the deep tone and no drone while cruising. Cold start sound is awesome but after warm up, the volume is just lightly louder compare with ODM exhaust. Overall a nice mod!

      PeterL

      Year: 2017 Submodel: GT

      Helpful (7)

    • 4/5

      Installation Time: Less than 1 Hour

      February 05, 2018

      Low Volume

      Mufflers and tips were great quality. I was running an x pipe/ muffler delete setup but got a fix it ticket here in CA. I decided to try these out and was not completely disappointed. Even with an x pipe these are VERY quiet compared to muffler deletes, Borla, Corsa, Roush, etc. On the other hand, this set up has no drone at all, and neighbors don’t hate me for cold starts at 6 in the morning. If your looking for a slight increase over stock go with these. If you want to make your car heard blocks away go with one of the louder systems out there.

      16GT

      Year: 2016 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      January 31, 2018

      Love them!

      Combined with an H-pipe it is produces an amazing deep sound. Just the perfect amount of noise.

      MiguelF

      Year: 2017 Submodel: GT

      Helpful (7)

    • 5/5

      Installation Time: Shop Install

      December 28, 2017

      Great sound

      Like everyone else buying mufflers without actually hearing them is difficult to say the least . If you want a deeper more throaty sound these are the ones for you ! I did not want them to be extremely loud . These mufflers were absolutely the right call !

      ToddB

      Year: 2016 Submodel: GT

      Helpful (7)

    • 5/5

      Installation Time: Less than 1 Hour

      December 04, 2017

      great sound, great fit

      easy to install looks killer quality parts sounds great

      LanceM

      Year: 2017 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      December 01, 2017

      Muscle sound!

      With the cat delete and a set of resonators and x pipe my car sound like a proper muscle car. Without the resonators everybody look at me LOL

      JavierC

      Year: 2017 Submodel: GT

      Helpful (8)

    • 5/5

      Installation Time: Less than 1 Hour

      November 18, 2017

      Very pleased

      Added these to my '16 GT combined with the Magnaflow Tru-X Resonator x-pipe and they sound great. Nice and deep at idle and low revs, but a nice bark when tacked up.

      RobertC

      Year: 2016 Submodel: GT

      Helpful (5)

    • 5/5

      Installation Time: Afternoon

      October 19, 2017

      AWESOME EXHAUST IMPROVEMENT....

      SLP loudmouth mufflers sound awesome with Ford race X-Pipe. I LOVE THE TONE. GET ON IT and IT SOUNDS MEAN. VERY PLEASED.!!!!!!

      MikeH

      Year: 2015 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      October 12, 2017

      Right on the money.

      Exhaust arrived on time, and decided to have shop installed. Took less than an hour and fitment was exceptional. Have a few friends running either muffler delete or resonator deletes (they like real loud) and even they were surprised how good it sounds. Zero drone, just what I was looking for. Well made.

      JH27

      Year: 2016 Submodel: GT

      Helpful (5)

    • 5/5

      September 14, 2017

      Neighbor Friendly

      I had an SLP exhaust on my '97 Trans Am and I was excited to see that 20 years later they're still in the game and have some options for the Mustang. I installed these with a Magnaflow Resonated X-pipe and the sound is quite subtle, yet deep and throaty. The two together give it a sound that has more growl than the stock exhaust of course but it is also very neighbor Friendly. It has no harmonic resonance (no drone) to worry about as well. If you are looking to be heard this is not the way to go. If you’re looking for that extra 'something' the way the Ford should have made it sound, then this might be a good option. I did knock a star off for fit and finish due to the ends (at the axle) being a bit squashed during shipping (hammered back into shape).

      BurnCycle

      Year: 2016 Submodel: GT

      Helpful (5)

    • 5/5

      Installation Time: Less than 1 Hour

      September 08, 2017

      Worth it

      I had straight pipes in the rear along with a x-pipe and the drone was outrageous. I added a set of these and it cleared it right up. Easy to install and look amazing. Sound pretty good as well. Do not regret one bit.

      JustinD

      Year: 2015 Submodel: GT

      Helpful (5)

    • 5/5

      Installation Time: Less than 1 Hour

      September 03, 2017

      Great sound gets louder over time.

      This kit along with an xpipe sound great . 6th gear drone is probably the only thing bad about them. So drop a gear and let her stretch out.

      DDsRedRoxanne

      Year: 2016 Submodel: GT

      Helpful (5)

    • 5/5

      Installation Time: Shop Install

      Installation Cost: 0-$100

      August 30, 2017

      Love it!

      I paired this with the SR X-pipe and I am very happy. I didn't want extremely loud but wanted it louder than stock. Really deep and clean sound with the X pipe. Hardly notice at cruising speed but you can hear it when you get on it! Not raspy at all with the x pipe either. Would highly recommend this setup for someone who doesn't want it too loud and for the money you can't beat it. Start ups are fun now!

      CalebG

      Year: 2016 Submodel: GT

      Helpful (7)

    • 5/5

      Installation Time: Less than 1 Hour

      August 03, 2017

      perfect sound and volume

      I will admit i was nervous buying this set up because we all know the traditional slp loud as heck raspy tone. However after several videos later i decided to but it anyway. I love this kit! this paired with my ford racing xpipe produces a fantastic tone and volume level. I dont regret this buy in the least and neither will you.

      csn95

      Year: 2017 Submodel: GT

      Helpful (6)

    • 5/5

      Installation Time: Less than 1 Hour

      May 10, 2017

      Great buy

      Installed these a couple days ago and this is how a muscle car is suppose to sound. Paired this with Ford racing x pipe and it's a little louder then expected but no regrets what so ever. Great buy

      BT

      Year: 2017 Submodel: GT

      Helpful (6)

    Related Mustang Categories