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Fox Body Mustang Cat Back Exhaust Installation Instructions (87-93)

Last Updated 10/13/2020 by Phillip Perez

Adding a cat back from LMR to your Mustang will not only increase HP, but will also make you stand out from the crowd. If you are in the market an aggressive sound look no further than a Fox Body cat back exhaust. Follow along in this simple step by step installation to ensure proper fitment and get your Fox back on the rode so you can enjoy that new cat back exhaust!

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How To Install A Fox Body Cat Back Exhaust (87-93)

Tools Needed:

Hacksaw or Sawsall
Common House Hold Tools
Welder(See Disclaimer)

Removal Instructions:

Using a hacksaw or sawsall, cut the stock tailpipes off, approximately 2” behind the muffler case. Separate the steel tailpipe hangers from the rubber mounts at the rear of each tailpipe. A lubricant may ease removal. Remove the stock tailpipes from the vehicle.

How To Install A Fox Body Cat Back Exhaust System (87-93) - How To Install A Fox Body Cat Back Exhaust System (87-93)

Support the stock mufflers with stands. Separate the steel muffler hangers from the rubber mounts at the rear of each muffler. A lubricant will usually ease removal.

Remove the two nuts at the muffler to catalytic converter flange connections. Remove stock mufflers from the vehicle.

Installation Instructions:

Before installing anything, prep the clamps supplied in the hardware kit by removing the nuts, and applying a thick lubricant such as white grease or anti-seize to the threads.

Position muffler into the stock location, on the right side of the vehicle. Slide the flange on the pipe up to the flange on the head pipe and reinstall the stock nuts onto the studs. Connect the hanger rod at the rear of the muffler to the rubber mount on the vehicle. Repeat this step with muffler on the left side of the vehicle. Note: If the studs do not line up with the holes there are two probable causes: The studs may have been bent from over tightening and can be straightened by bending back. There are also nuts on the back side of the studs that can be loosened, which will allow some adjustment of the spread.

Slip the right side tailpipe over the axle and into the right muffler outlet. Slide tailpipe hanger-rod into the stock rubber hanger at rear of the vehicle. Install a clamp and tighten enough to hold in place but still allow for adjustment. Repeat this step on the left side of the vehicle.

Adjust and align the position of all the pipes and mufflers to provide a satisfactory fit. Maintain at least 1/2” clearance around the new Exhaust System, the drivetrain and all chassis components. Also keep suspension travel in mind.

After the slip-fits have been welded, place the supplied hanger keepers onto the end of the hanger located at the rear of the tailpipes. Slide them up to the rubber mounts. This will hold the system securely in place.

Tip:

Disclaimer:
Not all exhaust systems will require welding. However, we recommend reading over the supplied instructions in your exhaust kit purchased from LMR. This will ensure proper installation of your Fox Body Mustang cat back exhaust.

About the Video

Fox Body Mustang Dynomax Ultra Flo SS Catback Install & Sound Clips (86-93 GT, LX)

Check out our YouTube channel for even more tech tips, installation videos, how-tos, and more. The best place to go for anything Mustang related!

Published on 2016-01-12
Dynomax’s cat back exhaust kits feature 2.5” aluminized steel constructed piping, easy installation and the tried and true Dynomax Ultra Flo muffler. This particular muffler is manufactured from stainless steel for lifelong durability and is completely polished for a show-quality shine.

The Ultra Flo muffler features an unrestricted, straight-through design and Dynomax’s proven CRF or Continuous Roving Fiberglass technology to absorb unwanted interior resonance while maintaining a deep performance exhaust tone.

All needed hardware is in the box with the only exception being the flow-tube to mid-pipe hardware since these will be re-used. This Dynomax Ultra Flo SS cat back will be available for two different Fox Body applications. One being 1986-93 LX cars and the other for 1987-93 GT Mustangs. So which ever kit you’re looking for be sure you select the correct one for your car.

Mustang Fitment: 1986 (86), 1987 (87), 1988 (88), 1989 (89), 1991 (91), 1992 (92), 1993 (93) LX, GT

Transcript
Hey! What’s going on everyone? Landan here with Late Model Restoration. Today this video is going to cover my quick overview of Dynomax’s Ultra Flo SS catback exhaust kit fitting your 1986-93 LX and GT Mustangs.

Dynomax is an industry leader when it comes to providing Mustang enthusiasts with high quality exhaust components. From complete exhaust systems to mufflers, Dynomax has what you need to get your Mustang sounding the way it should.

Dynomax’s cat back exhaust kits feature 2.5” aluminized steel constructed piping, easy installation and the tried and true Dynomax Ultra Flo muffler. This particular muffler is manufactured from stainless steel for lifelong durability and is completely polished for a show-quality shine.

The Ultra Flo muffler features an unrestricted, straight-through design and Dynomax’s proven CRF or Continuous Roving Fiberglass technology to absorb unwanted interior resonance while maintaining a deep performance exhaust tone.

All needed hardware is in the box with the only exception being the flow-tube to mid-pipe hardware since these will be re-used. This Dynomax Ultra Flo SS cat back will be available for two different Fox Body applications. One being 1986-93 LX cars and the other for 1987-93 GT Mustangs. So which ever kit you’re looking for be sure you select the correct one for your car.

Alright guys, follow along as I walk you through the detailed steps on installing Dynomax’s Ultra Flo SS cat back onto this pristine 1987 Fox with only seventy thousand original miles.

To begin installation, place the car on a lift or use a jack and jack stands. With the car in the air spray a penetrating catalyst on the flow tube to mid-pipe hardware. Allow the catalyst time to dwell before loosening the hardware. Since our factory cat back had some rust holes in it, we decided to cut some corners and make the over-the-axle pipes easier to remove. We cut the pipe right behind the muffler with a Sawzall. To help with removal from the exhaust hanger, spray some WD-40 onto the hanger.

If you have one, use an exhaust hanger removal tool to pop the metal hanger through the rubber at the rear of the car. Do the same for the other side. If you don’t have a special tool, just some good-ol-fashioned elbow grease will do just fine. Now, remove both over-the-axle pipes from the car. Use a 9/16” inch socket paired with a wobble to remove the mid-pipe to flow tube hardware. Again, use the hanger removal tool if you have one to help pry the metal hanger out of the rubber. Remove the rest of the factory exhaust from the car.

With both mufflers on the ground, remove the metal hangers with a 10mm socket. Carefully position your new Dynomax over-the-axle pipes. The hangers at the rear of the car will face toward the gas tank. Slide the metal hangers through the rear rubber insulator. Installation may be easier with a small application of WD-40 again. Our new Dynomax mufflers had a plastic covering over the polished stainless. Be sure you remove this covering from both mufflers.

Hit the front rubber insulators with some WD-40 and slide the hangers through the rubber with the ends facing out. Slide one of the included clamps over the rear pipe and then position the muffler. Slide another clamp onto the flow tube and then install the flow tube into the muffler. Loosely install the flow tube to mid-pipe hardware. Position the other muffler and flow tube, and then loosely tighten the hardware. Help from a friend may be needed when aligning the mufflers and tips. Loosely tighten the flow tube to mid-pipe hardware.

Before tightening all of the clamps, ensure that there is plenty of clearance between the piping and chassis. Align the tips and mufflers and then tighten down the flow tube to muffler clamps. Tighten the flow tube to mid-pipe hardware and then the muffler to over-the-axle pipe clamp. Now, reinstall the 4 previously removed hanger bolts onto the rear of the muffler. These will be self-threading into the new Dynomax muffler so make sure the holes are aligned on the hanger and muffler. Double check everything, and you’re all finished.

Well guys, you were probably wandering why we were putting a cat back on a perfect, low mileage Fox Body. As you could see, the stock exhaust for the most part had started to fall apart. This Dynomax kit was the perfect upgrade since it retains a nice subtle exhaust note. With that being said, let’s have a listen to what it sounds like.

If you’re on the hunt for a nice, subtle sound out of your Fox than this Ultra Flo SS kit from Dynomax is a must have. It installs with relative ease and is something you can do in your own driveway. Make sure you get the car as high as you can on the jack stands and this one should take you around 2 hours to complete.
A quick tip for any of you that have trouble removing the over-the-axle-pipes; simply remove both of the lower shock hardware and allow the rear end to hang. This will give you adequate clearance to get the current exhaust out of the way.
On the flip side, if the exhaust you are removing is useless, have some fun and cut that old junk with a Sawzall. This is obviously the easiest method to remove an old cat back that is no longer desired.

If you guys want to see more of the best install videos for your Fox Body Mustang, than I invite you to subscribe to our YouTube channel if you haven’t already done so. Don’t forget to head back over to the site and pick up a Dynomax Ultra Flo SS cat back for 86-93 LX or GT Fox Body at LMR.com!