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Flowmaster 40 Series Offset/Offset Oval Muffler - 2.5 in. (Universal Fitment)

AmericanMuscle no longer carries the Flowmaster 40 Series Offset/Offset Oval Muffler - 2.5 in. (Universal Fitment). Please check out Mustang Mufflers and Resonators for an updated selection.

Features & Details

  • Signature Flowmaster Sound
  • Original Two Chamber Technology
  • Offset Inlet and Outlet Design
  • 2.5" Inlet/Outlet Diameter
  • 409s Stainless Steel Construction
  • Sold Individually
  • Universal Fitment; Modifications Will Be Required
That Flowmaster Sound. Improve your Mustangs exhaust flow for an increase in horsepower and a deeper throatier exhaust note with a set of Flowmaster 40 Series Mufflers for a truly classic muscle car sound.

Superior Design. The Flowmaster 40 Series Mufflers are MIG welded from durable 16 gauge 409s stainless steel for durability and value. The 40 series mufflers use Flowmasters original two chamber design to increase power and sound. And each muffler is embossed with the "Flowmaster" name so you know it is the real article.

Modifications Required. This Muffler was designed to be used on mutliple applications, as it is not a direct fit replacement part. In order to install this Muffler properly on your vehicle, some modifications to the exhaust system will be required.

Application. The 40 Series Muffler's outer case measures 4" x 9.75" x 13", and features a 2.5" diameter inlet and outlet in an offset configuration. This is the perfect muffler for the 1979 to 2004 Mustangs. Excludes 1999-2004 SVT Cobra.

Fitment: 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 Details

MPN# 8042543

CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

What's in the Box
  • (1) Muffler
Installation Info
Tech Specs
40 Series Delta Flow versus 40 Series Original versus Super Flow 44 Series
  • Minimizes interior resonance
  • Aggressive exterior tone
  • Two Chambered Muffler
  • Made of Aluminized Steel
  • No minimization of interior resonance
  • Aggressive tone inside and out
  • Two Chambered Muffler
  • Made of Aluminized Steel
  • Delta Flow technology minimizes interior resonance
  • Aggressive deep powerful tone
  • Two Chambered Muffler
  • Made of Black Aluminized Steel
Will it fit my Mustang?
  • Bullitt - 01
  • Cobra - 93, 94, 95, 96, 97, 98
  • Cobra R - 95
  • GT - 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04
  • LX - 87, 88, 89, 90, 91, 92, 93
  • Mach 1 - 03, 04
  • Other - 79, 80, 81, 82, 83, 84, 85, 86
  • V6 - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04

    Customer Photos (2) Submit Your Photo

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      Questions & Answers (10)

      5 Top Rated Questions

      Will this produce a raspier or a deeper sound on an '04 V6?

      • Flowmaster exhausts will generally provide a deeper exhaust sound.

      Helpful (0)

      Is it street legal I am really trying to avoid getting pulled over by the cops buy still have some great sound

      • The Flowmaster 40 Series Offset Muffler will pass sound code regulations in most areas, however the remainder of your cars modifications, as well as the local regulations will mean that there is no guarantee this will pass local sound code regulations.

      Helpful (0)

      How loud is it I am looking for 95 decibels cause I don't want to get pulled over by the cops I need 2 of this. How many decibels will it be if I buy this

      • Hello! The Flowmaster 40 Series Offset Muffler does not have a decibel rating because the sound level will vary greatly depending on the application.

      Helpful (0)

      How many decibels is it I live in California and the limit here is 95 Decibels so the police won't pull me over

      • Hello! The Flowmaster 40 Series Offset Muffler does not have a dB rating, as it is dependent on the vehicle it is being used with.

      Helpful (0)

      Can this fit on a stock exhaust, can I just take out the muffler and just put the flowmaster one in?

      • Depending on the length of your stock muffler and the location of the inlet and outlet, this could be a direct replacement with the correctly sized clamps. If your stock muffler is shorter than the Flowmaster 40 Series Offset Muffler, additional cutting would be required.

      Helpful (0)
      Post Your Question
      5 More Questions
      Will these fit my stock 02 V6 mustang? 1 answer
      does the muffler have a hanger bracket on the rear of it like the factory muffler does 1 answer
      I currently own a '94 Cobra and would like to utilize the Flowmaster 40 series mufflers. Flowmaster no longer offers this muffler (instead they offer the 44 series muffler) in a full cat back exhaust set up. If I purchase two 40 series mufflers in 2.5in, the 2.5in Stainless Tailpipes (Part #20114), and the the 2.5in Flow Tube kit (Part #20109), will my muffler shop be able to build me a complete catback with these parts? Thank you! 1 answer
      does this product come with the exhuast tips? 1 answer
      Want the stainless steel flowmaster 40's. Are both sides the same? Are the flowmaster 40 mufflers for my 1989 mustang gt the same for both sides or is there a left and right muffler? I need the stainless 2.5". Thanks, Bruce 1 answer

        Customer Reviews (20) Write a Review

        Overall Rating 4.8

        out of 5 stars

        Installation Time:Weekend

        Installation Cost:$100-$250

        • Loudness / Volume 4.631579 4.6
        • Exhaust Note 4.789474 4.8
        • Fit & Finish 4.68421 4.7
        • Bang For Your Buck 4.789474 4.8



        • 5/5

          Installation Time: Afternoon

          November 01, 2017

          FLOWMASTER 40's (Stainless)

          My last set of 40's, 12 years old still sounded pissah but internals became loose. However they certainly exeded my expectations and money's worth! You will never hear ANYONE say that they aren't a great choice for all Mustang's period.

          WayneT

          Year: 1995 Submodel: V6

          Helpful (7)

        • 5/5

          September 20, 2017

          Perfect vintage sound

          Exactly what every "classic" 5.0 needs...two-chamber Flowmasters!

          WesD

          Year: 1995 Submodel: GT

          Helpful (6)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: 0-$100

          July 31, 2017

          Sounds great

          Replaced my old aftermarket mufflers with 2 of these great sound on my v6 mustang

          WilliamS

          Year: 2000 Submodel: V6

          Helpful (8)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: 0-$100

          February 16, 2017

          Best sounding Mufflers out there in my opinion

          Sounds great with h pipe nice well-built mufflers have had them on other cars in the past always a good sound

          JohnnyH

          Year: 2003 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Less than 1 Hour

          October 30, 2016

          Loud

          Tell all mustang drivers to put this on the stang.

          Rundown

          Year: 1994 Submodel: GT

          Helpful (7)

        • 5/5

          July 17, 2016

          Just what i expected

          Combined these with just a off-road h pipe no cat oem headers oem cam. Sounds great. gets complements all the time. Shipped fast easy fit.

          Sn95guy

          Year: 1994 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          May 28, 2016

          Flowmaster 40's on a 1993 Mustang GT

          Love these mufflers! Great aggressive tone. Installed these with the Flowmaster 2.5" exhaust pipes, Pypes 2.5" flow tubes, and BBK Catted H-Pipe (all purchased here from American Muscle) on our 1993 Mustang GT to replace the aging (and rusted) custom catted H-Pipe, MAC exhaust pipes, and Dynomax mufflers. At idle, these Flowmaster 40 mufflers sound more hollow and a little more aggressive than the Dynomax ones we had on there. Getting up to speed in 2nd and 3rd really makes this car sing now! Cruising in 5th sounds great but no major drone. Would highly recommend these! Not too raspy....perfect for that classic 5.0 Flowmaster sound!

          smldbowen

          Year: 1993 Submodel: GT

          Helpful (8)

        • 4/5

          Installation Time: Less than 1 Hour

          December 24, 2015

          Great Sounding Muffler

          If U want that Classic Mustang Sound Original 40 series Flowmasters are they way to go...I had the Super 44 and let me tell u don't waist your time on a Fox Body Original 40 series is the way to go...and they look great under the car!!

          MustangMain

          Year: 1993 Submodel: GT Memphis, TN

          Helpful (8)

        • 5/5

          Installation Time: Afternoon

          October 22, 2015

          Flowmaster exhaust kit

          Exactly what I wanted! My 1994 gt had a brand new exhaust on it when removed but it was all custom bent and looked TERRIBLE. This kit goes excellent with a bbk x pipe. I would recommend this to anyone and it bolt right in with no fabrication necessary. Looks more than professional when complete and sounds awesome! FANTASTIC PRODUCT! I would definitely buy this again if I bought another car

          Foxracer5824

          Year: 1994 Submodel: GT Petersburg, MI

          Helpful (7)

        • 5/5

          Installation Time: Afternoon

          August 27, 2015

          Hard to beat the sound on a 5.0 !

          Great fit, quick shipping, and a great price for a classic muffler! These sound amazing on the foxbody mustang.

          92gt

          Year: 1992 Submodel: GT mi

          Helpful (17)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          August 09, 2015

          Nothing beats it in a 5.0

          True 2 chamber 5.0 sound. Fast shipping and great price.

          JCD

          Year: 1988 Submodel: GT Richmond, Va

          Helpful (7)

        • 5/5

          Installation Time: Shop Install

          March 13, 2015

          Flowmaster 40 series stainless mufflers

          These mufflers are great! It's amazing how just changing out the stock mufflers can make my 4.6 sound so mean! They look great and have a nice classic, deep muscle car rumble.

          MaxPower

          Year: 2001 Submodel: GT Lakeland, FL

          Helpful (8)

        • 4/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          June 27, 2014

          Good Product

          Mustang has louder tone and note to it. Notice improvement!

          Lt535

          Year: 2004 Submodel: GT Big Stone Gap, VA 24219, USA

          Helpful (5)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          May 23, 2014

          killer sounds, defanetly a head turner

          drivin down the road i love that i can turn heads my giving my car the gas, the deep sound just fits the car great and im very happy with it

          mikesil44

          Year: 2002 Submodel: V6 RI

          Helpful (8)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: 0-$100

          April 18, 2014

          Perfect muffler!!

          This muffler is awesome. It makes your v6 sound much deeper and more aggressive. Not like those mufflers that will make your care sound like a ricer, this makes your v6 sound like a v8!

          2004v6mustang

          Year: 2004 Submodel: V6 Goodman, MO 64843, USA

          Helpful (7)

        • 5/5

          Installation Time: Afternoon

          October 18, 2013

          Awesome

          Installed these on my gt and sound amazing. I had them welded in bc clamps and adapters are a pain. Welding is the way to go !

          Jb02gt

          Year: 2002 Submodel: GT New York ny

          Helpful (6)

        • 4/5

          May 17, 2013

          SS 40 Series

          The only complaint I have is the mufflers don't have the hanger welded to it like the magnaflos had on the side closest to the rear axle. Other then the hanger missing its the best sounding muffler out there.

          kwmiked04

          Year: 2004 Submodel: GT shelton CT

          Helpful (8)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          November 08, 2012

          Awesome

          I've spent countless hours looking up exhausts and mufflers online! When I finally made my decision I choose the flowmaster 40 series mufflers in stainless steel. And let me tell u I couldn't be more happier! The sound is amazing! The stainless steel finish looks good too! I highly recommend this product to anyone who wants there car to come alive! Thanks AM!

          JayM99

          Year: 1999 Submodel: GT Whittier, CA, USA

          Helpful (8)

        • 5/5

          Installation Time: Afternoon

          September 21, 2012

          Awesome!

          Very pleased with my purchase. Way more aggressive sound and note than stock muffler. Flows much better also. Definitely recommend for anyone looking to make their 99-04 v6 more aggressive sounding.

          Caesarion

          Year: 1999 Submodel: V6 Michigan, USA

          Helpful (7)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: 0-$100

          August 06, 2012

          FLOWS !

          Best option for your stock muffelr replacement, not too loud, nice low rumble, perfect, sounds great under the V6.

          iSayWhtSheFeels

          Year: 2000 Submodel: V6 Indianapolis, IN, USA

          Helpful (9)

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