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Flowmaster American Thunder Classic Axle-Back Exhaust w/ Quad Tips (13-14 GT500)

AmericanMuscle no longer carries the Flowmaster American Thunder Classic Axle-Back Exhaust w/ Quad Tips (13-14 GT500). Please check out 2010-2014 Mustang Axle-Back Exhaust for an updated selection.
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Features & Details

  • Aggressive Flowmaster Classic 40 Series Sound
  • Polished Stainless Steel 3.5" Quad Tips
  • Durable 409 Stainless Steel Construction
  • Includes Two Flowmaster Mufflers
  • Direct Fit Replacement Upgrade
  • Made in the USA
  • Fits 2013-2014 Shelby GT500 Mustangs
Classic Flowmaster Sound. Give your 2013-2014 Shelby GT500 that unmistakable Flowmaster sound with a nice power boost with the American Thunder Axle-Back exhaust system. This system improves exhaust flow using Flowmaster's patented chambered muffler design for that throaty, aggressive exhaust tone your high powered Pony deserves.

Quality Construction. Made in the USA from durable 3" 409 stainless steel tubing for its resistance to corrosion, the Flowmaster axle back features two oval chambered Classic 40 Series Flowmaster mufflers with 3.5" diameter polished stainless steel quad tips for great muscle car looks and sound. As an added bonus the tip is embossed with the "Flowmaster" logo for true custom styling.

Direct Fit Upgrade. This Flowmaster American Thunder Classic Axle-Back Exhaust includes all the hangers and clamps needed to bolt  up in the stock location without any modifications required, making it a direct fit replacement upgrade.

Application. This Flowmaster American Thunder Axle-Back exhaust system is designed to fit the 2013-2014 Shelby GT500 models equipped with the supercharged 5.8L DOHC 32-valve V8 engine.

Fitment: 2013 2014 Details

MPN# 817612

CA Residents: WARNING: Cancer and Reproductive Harm -

What's in the Box
  • (1) Left Muffler
  • (1) Right Muffler
  • (4) Stainless Tips
  • (4) 2½” Band Clamps
  • (2) 3/8” Hanger Keepers
Installation Info
Tech Specs
Axle-Back Exhaust Specifications
Piping Material: 409 Stainless Steel Tip Material : Polished 409 Stainless Steel
Piping Size: 3" Tip Size: 3.5" quad tips
Muffler Type: Chambered Fitment: 2013-2014 Shelby GT500
Will it fit my Mustang?

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Customer Reviews (1) Write a Review

Overall Rating 4

out of 5 stars

Installation Time:Less than 1 Hour

  • Loudness / Volume 3 3
  • Exhaust Note 4 4
  • Fit & Finish 4 4
  • Bang For Your Buck 3 3

  • 4/5

    Installation Time: Less than 1 Hour

    June 04, 2014

    Brutally loud if you have an offroad midpipe. Subtle otherwise.

    Pro's: Easy to install. Lightweight compared to stock mufflers. Offer a unique exhaust tone. Con's (personal opinion): With my offroad H-pipe these mufflers were brutally loud & popped a LOT during downshifting. The exhaust tips look a bit small on the car. The tips are also 'unique' looking...some will like, some won't. Personally, if I keep this setup I'll definitely replace the tips with something else. Other: I felt the overall loudness of these mufflers with stock manifolds and midpipe was similar to the stock mufflers. However it does provide a unique, deeper tone and less of the 'burble' effect the stock gt500 mufflers produce. Note: You'll need a 16mm socket for the tip clamps (it's not mentioned in the installation instructions)


    Year: 2013 Submodel: GT500 South Carolina

    Helpful (2)

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