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Flowmaster American Thunder Cat-Back Exhaust (1998 GT, Cobra)

AmericanMuscle no longer carries the Flowmaster American Thunder Cat-Back Exhaust (1998 GT, Cobra). Please check out 1994-1998 Mustang Cat-Back Exhaust for an updated selection.
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Features, Video & Details

  • Aggressive Flowmaster Sound.
  • Super 44 Series Mufflers.
  • 2.5" Polished Stainless Steel Tips.
  • Mandrel-Bent Tubing.
  • Durable Aluminized Steel Construction.
  • Fits 1998 GT and SVT Cobra Mustangs.

Review & Installation Video

Review & Install Video

Hey I’m Justin with, and I’m checking out Flowmaster’s American Thunder Cat-Back exhaust, fitting the 98 Mustang GT, and Cobra. As you may know, Flowmaster offers a number of different mufflers, all with their own unique sound, in this case, the American Thunder for the 98 GT is built around my personal favorite Flowmaster offering, the super 44 two chambered muffler. There’s one muffler that really nails that iconic Flowmaster sound, this is it. This system is unique for a couple of different reasons: obviously for the use of those super 44 mufflers we just talked about, but also when it comes to the construction. The American Thunder uses 2.5” mandrel bent aluminized steel tubing, which may not be as good as stainless when it comes to resisting corrosion, but it’s definitely going to help keep the cost down versus that more expensive stainless steel. The tips are OE style 2.5” polished stainless steel, but as you can see that polished finish extends really far back, which is going to make for a nice clean finished look underneath the rear bumper. Because the exhaust hangers were designed differently on the 98, this exhaust will only fit the 98 GT and Cobra, unless of course you modify the hangers. Before getting started with the install, you will need to cut off your factory exhaust using a sawzall or something similar. Once you get that out of the way, getting the new Flowmaster bolted up should only take you about 2 hours from start to finish. Now let’s hear how the Flowmaster American Thunder catback sounds compared to our factory exhaust.

Flowmaster Sound.The Flowmaster American Thunder Cat-Back exhaust system with its mandrel bent tubing will improve your 1998 GT or Cobra Mustangs exhaust flow for an increase in power, and their included Super 44 Series Mufflers will improve your exhausts sound for a deeper throatier muscle car exhaust note.

Quality Construction. Constructed from mandrel bent 2.5" 16 gauge aluminized steel tubing for it's corrosion resistant properties the Flowmaster American Thunder Cat-Back features Super 44 Series chambered mufflers with 2.5" diameter OEM style polished stainless steel tips for muscle car looks and sound.

Fitment. This Flowmaster American Thunder Cat-Back exhaust system is designed to fit the 1998 GT or SVT Cobra Mustangs for both great looks and great sound.

Fitment: 1998 Details

MPN# 17215

CA Residents: WARNING: Cancer and Reproductive Harm -

What's in the Box
  • (1) Right muffler assembly
  • (1) Left muffler assembly
  • (1) Right tailpipe assembly
  • (1) Left tailpipe assembly
  • (2) Clamps
  • (4) Lock Washers
Installation Info
Tech Specs
Cat-Back Exhaust Specifications
Piping Material: Aluminized Steel Tip Material : Polished Stainless Steel
Piping Size: 2.5" Tip Size: 2.5"
Muffler Type: Chambered Fitment: 1998 GT or Cobra Mustangs
Will it fit my Mustang?

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Questions & Answers (3)

3 Top Rated Questions

Would these fit the 98 v6 bodt set up

  • The Flowmaster American Thunder Cat-Back Exhaust will work with a 1998 V6 if using a dual exhaust conversion H-Pipe or X-Pipe.

Helpful (0)

will this fit on pype's v6 dual catted x pipe?

  • Definitely! Once you have the true dual on your '98, you can then replace the catback portion of the Pypes conversion with any '98 GT catback of your choice. This Flowmaster would work with no problems!

Helpful (0)

Will this produce hook up to flowtech long tube headers and shorty mid pipe? I have a 1998 cobra and I am looking to do the whole exhaust in one big job.

  • You can install this catback along with any header/mid-pipe combination designed for your 1998 Cobra. The catback just bolts right up into the stock location!

Helpful (0)
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Customer Reviews (16) Write a Review

Overall Rating 5

out of 5 stars

Installation Time:Afternoon

  • Loudness / Volume 5 5
  • Exhaust Note 5 5
  • Fit & Finish 4.75 4.8
  • Bang For Your Buck 4.875 4.9

  • 5/5

    Installation Time: Afternoon

    September 19, 2017

    1998 Mustang

    The American Thunder exhaust has and awsome sound and install was easy. I purchase two 2/1/2 inch exhaust clamps that are much heavier duty other wise a great exhaust.


    Year: 1998 Submodel: Cobra

    Helpful (6)

  • 5/5

    Installation Time: Afternoon

    May 03, 2017

    Great sound!

    Great sound from the flowmasters! Truly the sound I was looking/hearing for! Only negatives are this is not a direct bolt on as I was expecting. Had to take it down to local exhaust/muffler shop to have the connecting flanges flared out more. After that it's a direct bolt on! Minus a star for that...


    Year: 1998 Submodel: Cobra

    Helpful (4)

  • 5/5

    August 10, 2016


    nice n loud and much better than stock. before it rattled like a can but not it sounds like a dragon.


    Year: 1998 Submodel: GT

    Helpful (6)

  • 5/5

    Installation Time: Afternoon

    May 25, 2016


    I purchased the flowmaster catback super 44 exhaust system. I was looking for that legendary flowmaster sound. But once installed I got one of the most unbelievably best sounding 2v mustangs around. The system bolted right up with no problems and when paired with my BBK off road h pipe. The legendary sound that flowmaster is known for and the deep roar of my h pipe gives it one unbelievable aggressive sounds I have ever heard by far on any 2v mustang. Thank you so much AM for selling me quality products every time!!


    Year: 1998 Submodel: GT

    Helpful (5)

  • 5/5

    Installation Time: Afternoon

    March 14, 2014

    Best add on ever!

    I have been a Flowmaster fan for years and after the satisfaction I recieved from this product I will be a customer for life! I am absolutley satisfied and blown away with not only the fit and finish but the sound and performance. I can not believe the heads that I turn!!!


    Year: 1998 Submodel: Cobra Janesville, WI, USA

    Helpful (5)

  • 5/5

    Installation Time: Afternoon

    February 22, 2014


    Fast shipping! Great product! Perfect growl! Installation took me less than 2 hours with my cousin. I like the tailpipes not too big or small, just great for a 1998! No regrets!


    Year: 1998 Submodel: GT California, USA

    Helpful (5)

  • 5/5

    Installation Time: Less than 1 Hour

    December 14, 2013

    Great Catback!

    Great catback! First start up I had a big smile on my face, haha. Coming from straight pipes, this is way quiet. When you step on it, you can hear the flows in action! Great for buck. Well worth it.


    Year: 1998 Submodel: GT Texas

    Helpful (7)

  • 5/5

    Installation Time: Afternoon

    November 29, 2011

    Great sound

    Great product, great sound, easy to install, and looks great.


    Year: 1998 Submodel: Cobra Mountain Home, ID

    Helpful (5)

  • 5/5

    Installation Time: Afternoon

    October 08, 2011

    The tips are amazing and the fitment was perfect!!!!

    I lifted the care at 11:00am and cut all old exhaust off and fit new ones in and bolted it on by 1:00pm.. 2 hrs for premium sound. It was and is amazing.


    Year: 1998 Submodel: GT Birdsboro PA

    Helpful (4)

  • 5/5

    August 14, 2011


    Have this set up on my stang with a custom h pipe! with the cam and work done to my engine, the sound is awesome !!! sounds like a true muscle car !! hate to brag but havnt heard a better sounding stang this summer !


    Year: 1998 Submodel: GT

    Helpful (3)

  • 5/5

    May 30, 2011

    Perfect Sound!

    Catted Tru-X Mid-pipe to Stock Ford cans had an annoying buzz. Installed Flow Master kit this weekend. Bolted up without a single issue. Annoying buzz is gone and the sound is perfect!

    Dan Robertson

    Year: 1998 Submodel: GT

    Helpful (5)

  • 5/5

    March 31, 2011

    Awesome Product

    First of all, I decided to buy this Catback from American Muscle because they had the cheapest price I could find. I ordered the product, and literally the next day I had it at my doorstep. I got it installed, and instantly noticed a difference with my Mustang. It was much louder, and just sounded like a pure beast (especially around 2k rpms!)It was just the sound I was looking for. I recommend buying this product from American Muscle, because I am so glad I decided to.


    Year: 1998 Submodel: GT

    Helpful (6)

  • 5/5

    October 14, 2010

    Classic Flows!!

    These sound awesome, especially paired with an offroad h-pipe. Fast shipping!! Great product

    Matthew Pauley

    Helpful (8)

  • 5/5

    May 14, 2010


    I bought this with the Mach O/R H pipe and with these two matched together, it sounds amazing! It gives you a nice deep tone, and doesn't give me any problems. Always having people tell me they love it.

    Justin D.

    Helpful (5)

  • 5/5

    March 13, 2010


    Great exhaust, paired with a mac o/r h-pipe sounds perfect. Classic mustang sound.


    Helpful (6)

  • 5/5

    February 08, 2010

    muscle car sound

    love flowmasters they sound great. the kit was high quality and the tips look good not to big like other companies out there. love the kit went on smooth no problems. nothing but great things!


    Helpful (10)

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