Flowmaster “Outlaw” Axle Back Exhaust Install

 Author: Curtis Bender

This article covers the installation of the Flowmaster “Outlaw” axle back on a 2014 Mustang GT but the same process works for most manufacturers’ axle back exhaust on all 2011-2014 Mustangs, V6, GT and 11-12 GT500.


One of the first mods that many Mustang owners do is change the exhaust for something with a little more presence. The OEM mufflers on the 2011+ Mustangs are actually pretty good and for stock mufflers, sound good too, but being the modding enthusiast that I am, like many Mustang owners are, I just can’t leave well enough alone, enter Flowmaster. Personally, I have not been much of a fan of the traditional Flowmaster exhaust sound. Maybe it’s that everyone and their cousin seems to have them on their old Chevy truck and they think that just because they have a rumbly exhaust, it makes them the fastest beast on the street. Things have changed though; Flowmaster is no longer a “one trick pony”! A while back Flowmaster developed some new mufflers, different from their standard offerings; such are the “Outlaw” race mufflers. The Outlaw muffler is a straight through design with a perforated center tube, minimal restriction and minimal sound reduction. Pairing these mufflers with the healthy performance engine in a Mustang makes for a very powerful exhaust note, one that profoundly announces your arrival!

To start this installation you’ll need to gain some working room, to this end, I used a pair of drive on ramps to raise the back of the car. Once on the ramps I let the car sit for a time to make sure the pipes and mufflers were cool enough to handle safely. During this cooling off period I pulled the new axle back exhaust out of the box and checked it over. One thing I noticed was that the polished stainless steel 4” tips on the ends of the outlaw mufflers had some specs of black paint on them (over-spray from the muffler paint process) and the polish wasn’t up to my expectations. To remedy this, I broke out some of my polishing supplies, a 6” buffing wheel and an arbor to mount it in my drill and a bottle of white polishing compound. The polishing compound took the specs of paint off as well as providing a terrific mirror polish shine to the stainless steel tips.

Following this I crawled under the back of the car to start the removal of the OEM axle back. The first thing I did was use a 15mm socket and an extension to remove the two bolts on the end of the panhard brace on the drivers side, just ahead of the muffler, and pulled the brace straight down, this gives you more room to maneuver the muffler around when removing it. Next, using a 13mm socket and extension, remove the bolt from the exhaust clamp on each muffler. You need to take the bolts completely out of the clamp so you can spread the clamp out enough to get it to slide over the ball end of the over axle pipe as you remove the muffler. Make sure to not lose these bolts or the small cylindrical nuts from the clamps as you will need to reuse them for the new mufflers.

Now for the fun part…

Some of the other installs I have seen show the person just grabbing the muffler and pushing a little and they pop the muffler right out of the front hangers with little effort, I did not find this to be the case. What I did to get the muffler loose from the car was to first slip the rear hanger rod from the rear hanger, then place my small aluminum floor jack under the exhaust pipes just ahead of the axle and jack the pipe up until it was against the floor of the car. I then spread the ends of the clamp on the muffler connection as far apart as I could which let the ball section of the over axle pipe separate from the muffler pipe. This still didn’t allow me enough room to get the hanger rods out of the front hanger so I decided to just unbolt the hanger from the car. On the drivers side, there are 3 bolts holding the hanger to the frame. Using the 13mm socket you can remove the bolt at the front and then working over the top of the muffler remove the rear bolt, then you can slide the muffler to the rear, exposing the bolt in the middle of the hanger, then using an extension and the 13mm socket you can remove that bolt. Be careful to support the muffler because when you take that last bolt out of the hanger the muffler will drop right out.

Repeat this procedure on the passenger side, noting the fact that there are only two bolts holding hanger to the frame on that side.

Once you have the mufflers out from under the car you can then transfer the hangers from the stock mufflers to the new mufflers. Next you will need to remove the clamps from the stock mufflers. The clamps are attached to the muffler with a small metal tab, best way to get them off is just to break them off by bending the clamp back and forth on that tab until it breaks. Then just slip the clamps onto the new mufflers in preparation for installing them.

With these outlaw mufflers, since they are so much smaller than the OEM mufflers, you will have much more room to work, making the install lots easier. Starting with the rear hanger, slip the rod on the muffler into the rubber and pivot the muffler up into position and bolt the front hanger in place. Next, you will want to slowly lower the jack under the exhaust pipe and guide the ball end into the end of the muffler pipe. Then slip the clamp up around the connection and put the bolt back in and snug it up making sure the clamp is centered over the connection but don’t fully tighten it. You then want to make sure the tip is centered in the bumper opening where you want it. Once you are satisfied with the tip alignment you can then finish tightening the clamp. Don’t forget to reinstall the two bolts in the end of the panhard brace. Then just repeat this process on the passenger side muffler and you’re finished, fire it up and check it out.

Now is when the fun really begins!!!

See the pics below…

One more thing, I weighed the OEM muffler as well as the Outlaw and there was quite a difference, OEM was 21 pounds, Outlaw was 8.4 pounds, over 25 pounds less for the pair compared to stock.

Tools needed: 13mm socket, 15mm socket, extension and ratchet (or impact wrench) 13mm combination wrench, floor jack, ramps.

Video here: