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Flowmaster 50 Series HD Muffler 8525554

Product Information
List Price:
Our Price:
5 (1 review)
Part #:
Body Style:
T409 Stainless Steel 18" Muffler | Dual Inlet & Outlet
2.5" Inlet & Outlet | 5" x 10" Body
2.5" Inlet / 2.5" Outlet | Dual In - Dual Out


  • Deep, Powerful Tone: The 50 HD mufflers if Flowmaster's most aggressive "50 Series" muffler. It offers a deep, powerful tone that sounds great and turns heads.
  • For Gas & Diesel Trucks: Flowmaster developed the 50 Heavy Duty muffler for both diesel and gas truck applications. Its open internal design offers increased performance for stock or modified trucks.
  • Increased Flow: The 50 Series HD muffler offers much greater exhaust flow to ensure increased power and mileage. The Heavy Duty muffler helps keep EGTs low and is well suited for towing applications.
  • Stainless Steel: Flowmaster mufflers are constructed of high grade stainless steel, which is corrosion resistant and will last the test of time.
  • Made in the USA - Santa Rosa, CA

The Flowmaster 50 Series Heavy Duty muffler was designed for full-size trucks with both gas and diesel engines. It features a 4" internal design to offer increased exhaust flow reducing restrictions and back pressure. This increased flow leads to significant gains in horsepower, torque, and fuel mileage.

The 50 Series HD mufflers is Flowmaster's most aggressive "50 Series" muffler and offers a deep, powerful that offers an incredible sound. It offers a performance sounding tone and is ideal for stock or modified trucks. The Flowmaster 50 Series Heavy Duty mufflers are constructed of stainless steel and feature an 18"Lx10"Wx5"H case with an overall tip to tip length of 24". The HD muffler is available for 3", 3.5", and 4" exhaust systems.

View Available Part Numbers For This Product Line

Frequently Asked Questions

What is Flowmaster's warranty? All Flowmaster products built of aluminized steel have a 10 year limited warranty against defective materials and workmanship. All stainless steel mufflers have a 10 year limited warranty against defective materials and workmanship.

What is "Delta Flow" technology?
Flowmaster's "Delta Flow" technology has evolved from extensive Research & Development at race-tracks around the country. This new technology provides superior scavenging while reducing resonance inside the vehicle. What you can expect is improved performance while maintaining a pleasant tone, both inside and outside the vehicle.

What materials are used to build Flowmaster mufflers?
All Flowmaster products are fully mig welded and built from 16 gauge aluminized steel for durability and value. Specific part numbers of the 40 and 50 series are also offered in 409 stainless steel, while the Hushpower II mufflers are offered in either 409 stainless steel, or 304 stainless steel.

What pipe size should I use for a street application?
In general, the following guidelines should be applied for street applications.

2" tubing up to 100 HP per pipe
2.25" tubing up to 160 HP per pipe
2.5" tubing up to 200 HP per pipe
3" tubing up to 300 HP per pipe 
What is the difference between a 40 series and a 50 series muffler?
Both mufflers have the same sound outside the vehicle, but each has varying sound levels generated inside the vehicle. The 40 series (two chambers) will resonate inside the vehicle, generally around 1800-2000 rpms and also again around 2400-2600 rpms. The 50 series (three chambers) incorporates an H-chamber that helps eliminate this interior resonance in the cab area of your vehicle.

Will I lose power going from a 40 series to a 50 series, or to a 70 series?
No. Flowmaster engineers each series of mufflers for very low restriction with the main differences being varying sound levels both inside, and outside your vehicle. This way you can customize your vehicles sound levels to your vehicles needs and sound preference.

Do I need to install an "H" pipe to my dual exhaust?
Flowmaster strongly recommends using an "H" pipe, commonly known as a "balance tube" on all "true dual" exhaust systems. An "H" pipe equalizes the pressures between both banks of the engine giving a broader and flatter torque curve throughout the rpm range. It also eliminates "back-rap" common on deceleration, and creates a deeper mellower tone both inside and outside of the vehicle.

Is an "X" pipe better than and "H" pipe?
Over the years, Flowmaster's testing of all types of crossovers, including "X pipes", has revealed no substantial benefits over a properly installed "H" pipe on street driven applications. However, in race applications with small cubic inch engines and /or restricted (small bore) carburetors, will respond well to the addition of X pipes, tri-y styled collectors and/or properly designed single exhaust systems.

Will my late model vehicle run better if I replace the single inlet muffler with a true dual exhaust system?
Flowmaster does not recommend replacing factory single inlet exhaust systems with a "true dual" system on computer controlled vehicles. The computers in most late model vehicles will not be able to compensate with the fuel needed with an almost doubling of the exhaust flow. Flowmaster’s dual outlet kits will give you the look of a "true dual" system, while optimizing the vehicles performance.

Do I need to run tailpipes after the mufflers?
Yes, Flowmaster highly recommends running tailpipes out from under the vehicle. This directs the exhaust fumes away from the vehicle, while minimizing the sound transmitted into the cab area of the vehicle.

What kind of performance gains can I expect when installing Flowmaster’s on my vehicle?
Performance gains will vary dependent upon your application. The more power the vehicle makes, the bigger the gains will be. Generally, a 5-7% gain of power is fairly typical, while 1-2 mpg can be achieved. That is if you can keep your foot out of the gas to hear that Flowmaster sound.

How can I be sure that I'm buying a Flowmaster muffler?
The Flowmaster name is embossed in every muffler case that Flowmaster builds. If it doesn't say Flowmaster on the case, it's not a real Flowmaster muffler.



Watch This Video
Flowmaster Exhaust Technology Explained - Chambered Technology 101


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Part #: FLM-8525554 Posted on
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(Alexandria, VA)
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This HD (Heavy Duty) muffler has a good aggressive sound. I recommend it for a truck/suv with a hemi or big engine.


Limited Lifetime Warranty

Flowmaster is offering a lifetime limited warranty on their stainless steel 50 Series HD Mufflers.


Flowmaster mufflers are designed to work with new or existing exhaust systems.  They offer slip on installation and can be welded or clamped into place.  Due to the use of heavier materials, Flowmaster recommends spot welding the joints when using clamps.  On some applications it will be necessary to cut or splice when adding Flowmaster mufflers to an existing exhaust system.