Talk to a Mustang Expert
1-888-332-7930
Mon-Thu 8:30a-11p, Fri-Sun 8:30a-9p

Free Shipping on Everything. Seriously. Details

Flowmaster Original 40 Series Offset Muffler - 2.5 in. (79-04 All, Excludes 99-04 Cobra)

38 Reviews
Our Price

$83.76

(each)
  • Item #18401
  • MPN# 42543

  • Market Price $94.65
  • You Save 12% ($10.89)
In Stock Ships same business day. Choose options to add to cart
Free Shipping on Everything
Customer Photos
Features
  • Signature Flowmaster Sound
  • Original Two Chamber Technology
  • Offset Inlet and Outlet Design
  • 2.5" Inlet/Outlet Diameter
  • Aluminized Steel Construction
  • Sold Individually
Description
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 2.5" 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

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
beats the ground

I have a 93 notchback with 3 in 2 chambers and they are super loud they beat the ground!

Helpful (1)

5/5
Nice sound and feel

Awesome sound! Get's loud up to about 2500 rpms but gets quiet once you're on the open road in 5th gear. Make sure you know your pipe size. I had to have midas custom fabricate part of my stock H pipes ...

Read More
Helpful (1)

Overall Rating 4.8 out of 5 stars
Read All 38 Reviews

Customer Photos (6) Submit Your Photo

View All 6 Photos

You Might Also Like

7 Questions / 4 Answers

Ask a Question

install when installing these do the existing short pipe piece on the muffler go over the stock pipes on the car? And can you use exhaust clamps instead of welding as a temp job?

Arthur

  • I actually welded these on my car 3.5 years ago, and unfortunately do not remember for sure, but I think welding them is the only option.

    MineralGreyGT

    Good Answer (0) (0)

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

2? Im new to the whole muffler system my cobra has one and it sounds nice. My fiance has an 04 gt and im going to get her this one but do i need to buy 2? or just 1 all help appreciated

forty

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

I have a 1997 Mustang Cobra and i noticed these flowmasters come in 2.5 IN and 2.25 IN which ones do i need?

Anarchy

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

More Products You Might Like

Customer Reviews (38) Write a Review

Overall Rating 4.8

out of 5 stars

Installation Time:Full Day

Installation Cost:$100-$250

  • Loudness / Volume 3.882353 3.9
  • Exhaust Note 4.411765 4.4
  • Fit & Finish 4.588235 4.6
  • Bang For Your Buck 4.588235 4.6



  • 5/5

    July 25, 2016

    Flowmaster 40

    If you're like me who owns a v6, you are always looking for ways to look and sound like the big boys. Well, these plus Mac long tube headers = OMG. I've never thought that my little 3.8 could sound good. Deep rumble at idle and tons of neck breaking when driving down the road. I would recommend these two products for anyone who has a v6 and want the v8 burbly sound. Hands down the mid I've ever done to my car!

    Stabgfan99

    Year: 1999 Model: V6 Driving Style: Daily Driver 'Stangs I have owned: 1

    Helpful (1) (0)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $250-$500

    May 13, 2013

    go all out

    I have 40s on every muscle car I have and to make sure my 02 gt could compare with the sound of the 60's muscle since its legal where im at I completely changed the exhaust removed the cats and did straight pipe back with the 40's and even the tiny v8 in the new edge mustang can keep the sound of a big block

    borocamo

    Year: 2002 Model: GT Driving Style: Daily Driver 'Stangs I have owned: 4 Fruita, CO, USA

    Helpful (1) (0)

  • 5/5

    July 10, 2011

    Flowmaster

    Make my car sound great. People think my v6 sounds like the GT. Thanks American muscle

    Jayce

    Year: 1999 Model: V6 Driving Style: Daily Driver

    Helpful (1) (0)

  • 5/5

    February 26, 2011

    Nice sound and feel

    Awesome sound! Get's loud up to about 2500 rpms but gets quiet once you're on the open road in 5th gear. Make sure you know your pipe size. I had to have midas custom fabricate part of my stock H pipes to fit them. 2.5 inch pipes and 3 inch tips

    Ryan

    Year: 2004 Model: GT Driving Style: Daily Driver

    Helpful (1) (0)

  • 5/5

    November 19, 2010

    beats the ground

    I have a 93 notchback with 3 in 2 chambers and they are super loud they beat the ground!

    austin dukes

    Year: 1993 Driving Style: Street / Strip

    Helpful (1) (0)

  • 5/5

    May 05, 2010

    original 40 series flows.

    Great company, come here for all your mustang needs.

    Josh

    Helpful (1) (0)

  • 5/5

    July 10, 2010

    Takes some time

    I had 44's on but nowhere near the same sound as the original flow 40 series...going through tunnell's is heaven and shifting at 2500 rpms is heaven sent lol they were a tad quiet at first but after 100 miles there starting to wake up!! dont get any but the original flows!!

    Co

    Helpful (38) (3)

  • 5/5

    April 05, 2010

    Classic 40s

    I had these welded in today they sound incredible I have the stock h pipe with cats and it is still nice n loud, it has a great deep tone and it was a great 1st mod for my car. 2200 RPM is the sweet spot.

    Dale P

    Helpful (24) (2)

  • 5/5

    February 25, 2010

    great mufflers

    I put on a pair of Flowmasters and what a difference they made in sound and horsepower. Getting these mufflers along with a cold air intake and your mustang will improve performance 100%. I recommend these mufflers to other mustang owners.

    Chris

    Helpful (22) (2)

  • 5/5

    August 27, 2010

    Great sound

    Installed Original 40 Flowmasters and am very please with the sound. The only problem I had was I had to adapt the flanges to my orginal equipment pipes. Be sure you know what size pipes you have before ordering.

    Bob

    Helpful (18) (1)

Related Mustang Categories