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Flowmaster Original 40 Series Offset Muffler - 2.25 in. (79-04 All, Excludes 99-04 Cobra)

Market Price $94.65 You Save 12% ($10.89)

$83.76 (each)

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  • Item 18458
  • MPN# 42443

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Features & Details

  • Signature Flowmaster Sound
  • Original Two Chamber Technology
  • Offset Inlet and Outlet Design
  • 2.25" Inlet/Outlet Diameter
  • Aluminized Steel Construction
  • Sold Individually
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 aluminized 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.

Application. The 40 Series Muffler's outer case measures 4" x 9.75" x 13", and features a 2.25" 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

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
  • Foxbody - 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93
  • Mach 1 - 03, 04
  • V6 - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04
  • Cobra - 94, 95, 96, 97, 98
  • GT - 94, 95, 96, 97, 98, 99, 00, 01, 02, 03, 04

Most Helpful Reviews

5/5
Definite bang for the buck.

I can't afford to fully upgrade to a true duel exhaust, so I kept my single exhaust. I bought this muffler and grabbed an exhaust tip that didn't look like the rusty stock tip, had a local guy install ...

Read More
Helpful (3)

5/5

Great sound!

These flowmaster 40's gave me the perfect sound for my mustang. I was dealing with to much drone and these cleared it up nicely.

Helpful (2)

Overall Rating 4.7 out of 5 stars
Read All 7 Reviews

Customer Photos

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3 Questions / 6 Answers

Ask a Question

Do I get the 2.25 or the 2.50 for a bone stock 2004 mustang gt cause i thought the GT had 2.5?

Psoul

  • Psoul, From all I find the GT has the 2.5 Inlet. You can go to your friendly Auto Parts store and have them verify - takes a couple of minutes - Give them Make, Model, Year, Engine size, etc... Hope this helps, BobH98

    BobH98

    Good Answer (0) (0)

Show 1 more answer Answer This Question I need this answered (0) (0)

I want a flowmaster but I prefer a not too loud somebody can help me , is my first mustang and I don't have experience with the mustang 88

Omar777

  • This exhaust will give you a deep, throatier exhaust note, but it won't be overly loud. It might be easier to give our customer service a call so you can discuss what it is you're looking for and we can offer some suggestions. Hope this helps!

    LisaS

    Good Answer (0) (0)

Show 2 more answers Question Resolved

How much hp does this add and is it more with dual exhaust? I have a 2000 v6 with a dual exhaust and i was wondering how much hp each of these add? and since i have a dual exhaust im going to buy two of them so how much hp would they add with two of them?

TimmyTim97

  • People rate mufflers for +5-10HP, It is really nothing noticeable. The biggest improvement is in the sound. And you would need 2 of these for dual exhaust.

    chriscarr86

    Good Answer (0) (0)

Answer This Question I need this answered (0) (0)

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Customer Reviews (7) Write a Review

Overall Rating 4.7

out of 5 stars

Installation Time:Afternoon

Installation Cost:0-$100

  • Loudness / Volume 4 4
  • Exhaust Note 4.428571 4.4
  • Fit & Finish 4.571429 4.6
  • Bang For Your Buck 4.428571 4.4



  • 5/5

    Installation Time: Shop Install

    Installation Cost: 0-$100

    June 12, 2013

    Definite bang for the buck.

    I can't afford to fully upgrade to a true duel exhaust, so I kept my single exhaust. I bought this muffler and grabbed an exhaust tip that didn't look like the rusty stock tip, had a local guy install it, and for the money this muffler really delivers on a single exhaust V6. It isn't obnoxiously loud, but it's definitely less subtle than the stock muffler, mainly under acceleration of any sort. I paid around $200 total for this upgrade, and it was worth it. I don't think I'm going to be keeping my mustang for much longer, but this is going to make the remaining time with it more enjoyable.

    BoomBoxBoy23

    Year: 2004 Submodel: V6 Warrenton, VA, USA

    Helpful (3) (0)

  • 5/5

    Installation Time: Afternoon

    February 14, 2013

    Great sound!

    These flowmaster 40's gave me the perfect sound for my mustang. I was dealing with to much drone and these cleared it up nicely.

    JoeR990

    Year: 2001 Submodel: V6 King of Prussia, PA, USA

    Helpful (2) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    May 30, 2015

    Muffler

    Sounds great. Best purchase yet. Love it highly reccomend this product. Makin heads turn left and right.

    Joshie

    Year: 2000 Submodel: V6 Winslow, ME

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    December 18, 2013

    Amazing Rumble 93 Mustang LX 5.0

    The quality of the product far surpasses that of what i expected. theres no doubt i made the right choice when choosing flowmasters.

    Diego725

    Year: 1993 Submodel: Other Los Angeles, CA, USA

    Helpful (1) (0)

  • 5/5

    Installation Time: Less than 1 Hour

    November 11, 2013

    01 gt automatic

    These mufflers sound really good with o/r x and mac longtubes ecpecally goin threw tunnels real deep and throaty

    morganp21

    Year: 2001 Submodel: GT Jasper, AL, USA

    Helpful (0) (1)

  • 4/5

    Installation Time: Less than 1 Hour

    April 20, 2013

    Great sound, not too loud!

    I had these mufflers installed to my stock pipes for $80 at a local shop. They have a great sound! Deep, throaty, aggressive, not too loud. Already gotten compliments on the road. These mufflers gave my GT the classic muscle car sound I was looking for. Thanks AM!

    NCchris

    Year: 2000 Submodel: GT Greensboro, NC, USA

    Helpful (0) (2)

  • 4/5

    Installation Time: Afternoon

    November 04, 2016

    1995 V6

    This muffler is pretty nice. I have a 95 v6 that I put this on, it gave it a pretty good rumble by just leaving the stock Y pipe setup I just took the old (single) muffler out and replaced it with this one. I took it to a local muffler shop and for about 40-50 bucks and 30 to 45min my car was sounding a bit meaner. I mean it still doesn't purr like a v8 but overall great part, cheap and relatively easy to install.

    Bgv6vert

    Year: 1995 Submodel: V6

    Helpful (0) (0)

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