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Flowmaster American Thunder Cat-Back Dual Dump Exhaust - Stainless Steel (86-98 GT, Cobra)

Market Price $415.99 You Save 13% ($55.02)
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  • Item 18431
  • MPN# 817574

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Features, Video & Details

  • Aggressive Flowmaster Sound
  • Dual Dump Exhaust
  • Super 44 Series Mufflers
  • Mandrel-Bent Tubing
  • 409 Stainless Steel Construction
  • Fits 1986-1998 GT and Cobra Mustangs

Review & Installation Video

Review & Install Video

Hey, Justin here with, breaking down Flowmaster’s American Thunder Cat-Back Dual Dump exhaust fitting the 86-98 GT and Cobra. Obviously the big difference between this system and other exhausts is the way it exits, as you can see there are no real tail pipes. Instead, everything flows with these super 44 series mufflers, through the turn downs and then dumps right out underneath the car right in front of the rear axle. So why would you want to do this? Well, some would say it gives the rear of the car a different, some might even say cleaner look by deleting those tail pipes altogether, there’s no real difference in performance to speak of, although it might be slightly louder inside the cabin versus your standard tail pipe. As for the system itself, we’re looking at a full 409 grade stainless steel construction throughout, and what little piping there is has all been mandrel bent. That iconic Flowmaster sound comes courtesy of Flowmaster’s twin super 44 series mufflers which Flowmaster claims is one of the most aggressive mufflers they offer in terms of overall sound. Because Ford chose to weld the factory exhaust on the Fox bodies and the SN95’s, you will need to cut it off with a sawzall or something similar before getting started with the install. Once you get that out of the way, getting the new Flowmaster bolted up is a pretty straightforward task that should only take you about 2 hours from start to finish. Now let’s hear how Flowmaster’s dual dump American Thunder sounds compared to our factory exhaust.

Flowmaster Sound. The Flowmaster American Thunder Cat-Back Dual Dump exhaust system with its mandrel bent tubing will improve your Mustangs exhaust flow for an increase in power, and the included Super 44 Series Mufflers will give your Pony a deep throaty muscle car exhaust sound.

Dual Dump Exit. This Flowmaster American Thunder Cat-Back system features a Dual Dump design that exits the exhaust in front of the rear wheels for a stealthy appearance.

Stainless Steel Construction. Constructed from mandrel bent 2.5" diameter 16 gauge stainless steel tubing for it's corrosion resistant properties the Flowmaster American Thunder catback features Super 44 Series chambered mufflers for that classic muscle car sound.

Application. This Flowmaster American Thunder Stainless Steel Cat-Back Dual Dump exhaust system is specifically designed to fit the 1986 to 1998 5.0 LX, GT and SVT Cobra Mustangs.

Fitment: 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 Details

What's in the Box
  • (1) Left muffler assembly
  • (1) Right muffler assembly
  • (2) Turn down pipes
  • (2) Clamps
  • (2) Hanger keepers
Installation Info
Tech Specs
Cat-Back Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : N/A
Piping Size: 2.5" Tip Size: N/A
Muffler Type: Chambered Fitment: 1986-98 GT and SVT Cobra Mustangs
Will it fit my Mustang?
  • Cobra - 94, 95, 96, 97, 98
  • Foxbody - 86, 87, 88, 89, 90, 91, 92, 93
  • GT - 94, 95, 96, 97, 98

People Who Bought This Item Also Bought

Most Helpful Reviews

Great sound

I replaced the SLP exhaust with this. It sounds deeper and much less raspy. I love the sound! Cabin noise is louder since these dump under the rear seats

Helpful (1)

Sounds great

Sounds good, install was easy as it replaced rusted and banged up "aluminized" flowmasters with dumps. These tuck up real nice unlike the homebrew setup that was in there before. My car is a 5 speed ...

Read More
Helpful (1)

Overall Rating 4.7 out of 5 stars
Read All 13 Reviews

Customer Photos (3) Submit Your Photo

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6 Questions / 10 Answers

Ask a Question

Will this setup allow exhaust gases into the car?


Helpful (0)
  • No, these dump right by the rear differential which is behind the passenger compartment.


Can the tips be angled slightly out to allow more clearance for lowered cars? My mufflers are already very closed to the ground.


Helpful (0)
  • The tips are already bent to point downward. You can try and turn them sideways to see if that allows clearance. Or you may have to bend the tubes in order to get the proper clearance. In that case, it will involve doing some modifications.


Will this not allow my fox to pass the heavily regulated emissions laws in california?


Helpful (0)
  • The Flowmaster American Thunder Cat-Back Dual Dump Exhaust - Stainless Steel (86-98 GT, Cobra) will have a CARB number associated with it as it is not a CARB restrictive exhaust.


Fitment? I just took these off my totaled 1996 Cobra and wanted to know if it would fit on a 2003 Cobra?


Helpful (0)
  • I would say no. I do not believe these will fit any Mustang post 98.


Show 1 more answer

Loudness On a scale outta 1-10, 10 being the loudest. How loud would a 95 GT with a full length BBK Catted X and these dumps? I think with these dumps and the catted x it should be pretty loud and mean right?


Helpful (0)
  • 10, mine are louder then Boral stingers with no cats, inside vibrations are extremely high. The dumps echo off the street so the sound is amplified and deep. Its really mean sounding, and at WOT sounds amazing!!!


Show 2 more answers

Turn down vs tail pipes Is there a HP diff with the turn downs vs full lenght tail pipes on a 97 GT?


Helpful (0)
  • No. It is merely a matter of preference in styling.


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Customer Reviews (13) Write a Review

Overall Rating 4.7

out of 5 stars

Installation Time:Afternoon

  • Loudness / Volume 4.545455 4.5
  • Exhaust Note 4.818182 4.8
  • Fit & Finish 4.909091 4.9
  • Bang For Your Buck 4.818182 4.8

  • 5/5

    September 09, 2016

    Great sound

    I replaced the SLP exhaust with this. It sounds deeper and much less raspy. I love the sound! Cabin noise is louder since these dump under the rear seats


    Year: 1996 Submodel: GT

    Helpful (1)

  • 3/5

    August 08, 2016

    Not what I thought it would sound like.

    It is a good sound it's just not what I thought it was going to sound like. I was expecting a more deep raspy sound but it sounds not as good especially on a automatic


    Year: 1997 Submodel: GT

    Helpful (1)

  • 4/5

    Installation Time: Less than 1 Hour

    June 29, 2016

    Sounds great

    Sounds good, install was easy as it replaced rusted and banged up "aluminized" flowmasters with dumps. These tuck up real nice unlike the homebrew setup that was in there before. My car is a 5 speed and I love the sound; but, I suspect it would be annoying with an automatic, I could see it droning. The fact that they dump under the car also makes them louder inside as well as giving it a more hollow sound vs going out through the tailpipes. The only reason this got knocked down a star is that I think it should have come with new hardware to bolt the mufflers to the H pipe. I'd plan on spending about $30 on stainless hardware to install. Otherwise, sounds great, my car no longer scrapes going over speed bumps and I wont have to replace these after a few years from rust.


    Year: 1987 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    August 08, 2012

    Great sounding mufflers!

    Installed these along with the Pypes off-road x-pipe and I am extremely satisfied. Bolted right up in place with no install problems. Only problem with turndown tips is ground clearance, but my car is also lowered a bit. My 96 GT rumbles nice And loud when I'm idling and driving. Head turner!


    Year: 1996 Submodel: GT Honolulu, HI, USA

    Helpful (2)

  • 5/5

    Installation Time: Less than 1 Hour

    March 23, 2016

    97 mustang gt

    Love the sound of it ! It gives it a deep sound ! Very easy to install! Very happy with them!


    Year: 1997 Submodel: GT

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    January 14, 2016

    Perfect exhaust for a big tire car!

    Bought this setup because the 315's on my 95 GT rubbed the tailpipes. Only problem I ran into was the bracket in the drive shaft tunnel that holds the brake line rubbed the passenger side pipe between the muffler and the end of my H pipe. I trimmed that bracket a little and no more rubbing. As far as sound I have factory exhaust manifolds with aftermarket H pipe with high flow cats and it's actually quieter going down the road than the exhaust I took off which surprised me. Only time I get the high interior drone sound is between 1000-1800 rpm's. Going down the highway in 5th gear and stock gears and it's nice and mellow. Low RPM's is where all the noise is. Exhaust note is great, definitely recommend!!


    Year: 1995 Submodel: GT Mebane, NC

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    December 23, 2014

    Driveway Install.

    The Flowmaster American Thunder Catback Dual Dump exhaust system looks and sounds great. I was able to install the system in my driveway in one afternoon. The bolt hole alignment was a bit off and took awhile to get it just right to be able to install. Overall this system looks great and sounds even better, I could not be happier.


    Year: 1994 Submodel: GT Prescott, AZ, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    December 18, 2014

    easy install sounds great

    this was the easiest install i have ever done . and it sounds great


    Year: 1992 Submodel: Other Philadelphia, PA, USA

    Helpful (1)

  • 4/5

    Installation Time: Afternoon

    December 21, 2013

    flowmasta dumps

    Very cheap product and great bang for the buck. Have this mated to longtube headers and an x pipe and the sound is just mean. I recommend


    Year: 1995 Submodel: GT bay area

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    August 28, 2013

    Pretty mean sound !!!

    These flowmasters were easy to install very simple. I like them they really sound great n loud the only thing is that in the inside of the car is it rattles everything but I don't mind . I have em on bbk short headers n a bbk x pipe fits perfect .


    Year: 1994 Submodel: Cobra Crane, TX 79731, USA

    Helpful (1)

  • 5/5

    Installation Time: Afternoon

    May 03, 2013

    Easy install, great product!

    Another great product from flowmaster! Bolted up perfectly to my BBK xpipe, and has an awesome aggressive sound! It is a little louder inside the car, but not too bad. Don't miss the tail pipes, and love the cleaner look! I recommend this product! THANKS AM!


    Year: 1998 Submodel: Cobra Illinois, USA

    Helpful (1)

  • 5/5

    Installation Time: Less than 1 Hour

    June 15, 2012


    I actually didn't purchase this exhaust off of American Muscle, because they just started selling recently, but I just did the install today. I installed it with the BBK O/R H-Pipe and it sounds absolutely amazing! Bolts right on, nice and easy. I had no issues whatsoever. I replaced my old hanger with new ones during the install, and I installed the new H-Pipe at the same time. This setup that I am running has an amazing increase in throttle response and overall horsepower. If you are afraid that you won't gain enough, let this be your reassurance. I absolutely love the way they sound.


    Year: 1994 Submodel: GT Topeka, KS, USA

    Helpful (2)

  • 5/5

    Installation Time: Afternoon

    August 15, 2015

    Very Nice Exhaust for A Good Price

    The install went great with out any problems, The only hiccup is that the holes leading to the x pipe are a little small buy we just filed out the holes and it fit perfectly. Also its a nice deep muscle car sound low growl with my catted h-pipe.


    Year: 1998 Submodel: GT Orefield, PA

    Helpful (0)

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