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Flowmaster American Thunder Axle-back Exhaust System - Active Valves

Fits 2018-2021 Mustang GT 5.0L without Factory Active Performance Exhaust Valves.

Part # 817859 Be the first to write a review
Estimated shipping date: 02/04/2022
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Delta Flow
Introducing our new American Thunder® Axle-back exhaust system featuring our new W.A.V.E. Technology™ (Wireless Active Valve Exhaust™) for all 2018-2021 Ford Mustang GT 5.0L coupes and convertibles, originally equipped WITHOUT the Factory Active Performance Exhaust Option. This trick new stainless steel exhaust system has two wireless remotes that control the high-quality actuators and exhaust valves included with the specially designed mufflers incorporating Outlaw® muffler technology. When the valves are closed, you have a moderate exterior and interior tone. Want more sound? Push the remote and the valves open for an aggressive wide-open's that simple! Other features include large 3.00-inch mandrel-bent 409S stainless steel tubing for high flow and durability. The system is finished off with quad 4.00-inch polished 304 stainless steel tips for an aggressive look that demands attention. Includes all necessary parts, hardware and detailed instructions for an easy installation you can do at home. Covered by the Flowmaster® Lifetime Limited Warranty. Want even more sound? Be sure to check out our Scavenger Series® no resonator X-Pipe kit #817817. Notes Fits coupes and convertible models.


  • Includes Two Wireless Controllers to Open/Close Valves
  • Comes with High Quality Valves and Actuator Motors
  • Mandrel-bent 16 Gauge Stainless Steel Tubing
  • Quad 4.00-inch Polished Stainless Steel Tips
  • Featuring Race-proven Outlaw Technology
  • Uses the Factory Hanger Locations
  • Deep Powerful Exterior Sound
  • Lifetime Limited Warranty
  • Open Exhaust Sound
  • W.A.V.E. Technology
  • Easy Installation

About Flowmaster

Flowmaster® is a household name, and for good reason. They've built legendary exhaust systems and mufflers for decades, and now offer performance air intakes, catalytic converters, and headers to give your hot rod performance to match the iconic Flowmaster sound.

Brand Flowmaster
Catalytic Converter IncludedNo
Emission Code5
Exhaust SeriesAmerican Thunder
Exit PositionDual Out Rear
Heat ShieldNo
Material409 Stainless Steel
Mount TypeUses Factory Hangers
Muffler Body Length (in)11
Muffler ColorBlack
Muffler FinishPainted
Muffler Inlet Diameter3
Muffler Inlet LocationOffset
Muffler Material409S Stainless Steel
Muffler Outlet Diameter3
Muffler Outlet LocationDual Outlet
Muffler Part NumberKit Only
Muffler Quantity2
Muffler Series60 Series
Muffler ShapeOval
Muffler TypeReflection
Product TypeExhaust System
Single DualDual
Sound LevelAggressive
System TypeAxle-back
Tip CutAngle
Tip Diameter4
Tip Edge StyleCut
Tip FinishPolished
Tip Length5.25
Tip LogoEmbossed
Tip Material304 Stainless
Tip ShapeRound
Tubing Diameter (in)3
Tubing Material409S Stainless Steel
California Proposition 65 Chemical NameChromium (hexavalent compounds)
Nickel (Metallic)
California Proposition 65 RequiredYes
Part Number817859

This part is legal for sale or use on Emissions Controlled Vehicles, Uncontrolled (Non-Emissions Controlled) Vehicles, and Racing Use Only Vehicles because it does not affect vehicle emissions and is not covered by emissions regulations.

Fits 2018-2021 Mustang GT 5.0L Coupes & Convertibles without Factory Active Performance Exhaust Valves.

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    Some parts are not legal for use in California or other states with similar regulations.