We recommend Internet Explorer set to 1024x768.

© 1998 Brian F. Schreurs
Even we have a disclaimer.

Buy our book!

Fortunately, cat-back exhaust systems are not very hard to install, but it is definitely a two-person job. A visiting 1995 Mustang GT offered a chance to see for ourselves. We used a Flowmaster American Thunder (#17212) cat-back system with two-chamber mufflers and polished tips. The instructions say it's not necessary to weld the pipes, but of course you can if you want. We contacted a local exhaust guru and he said it was not necessary.

Yeah -- that's gotta go.

First of all, read over the instructions but don't take them too seriously. Especially the application references; they're inconsistent. It'll fit. Don't worry.

The first thing we did was jack the car too high in the air. Ground clearance to work is a real problem; putting jack stands under the axle hardly leaves any crawl space up by the cats. Our solution was to put the stands under the shock mounts. Now there's plenty of room to work.

With the car in the air, it's time to take apart the stock exhaust. There is a rubber isolator connecting the tailpipes to the chassis; the pipes must be pulled free. But, good ol' Ford put a nub on the end of the stock hangers so it's quite difficult to pull them free.

Looks easy from here, doesn't it? A lot of WD-40, prodding, and jiggling will eventually separate the tailpipe from the isolator.

Get out your friend Mr. WD-40. Apply liberally to the isolator. Have one person push against the isolator with a screwdriver (toward the outside of the car) while another person wiggles the hell out of the tailpipe, pulling back and forth but with more emphasis toward the center of the car. This works the WD-40 into the isolator and, eventually, it will come free. Trust us.

Now for the best part. Ha ha ha. Get a new hacksaw, or preferably a cutting torch or sawzall. Cut the tailpipes off, about two inches downstream from the mufflers. If you are using a hacksaw (like we were), count on this taking about one hour per pipe.

If you cut the pipes in the right place, you should be able to slide them out from under the car without too much trouble. It takes a bit of fiddling, but they'll come free.

Get further under the car. Unbolt the muffler inlet pipes from the flanges behind the cats (we know, the instructions say to undo the muffler's insulator first; trust us on this one, they're wrong). We soaked them in WD-40 first, but, to be fair, they came off so easily we doubt they needed it.

If you make your cut right about here, you'll be in fine shape.

There should be enough give in the muffler's hangers to allow you to pull the pipes free of the flanges. Now you'll be able to move the mufflesr around while you...

Pull the muffler hangers free of the insulators. Here are some tips. Ignore the instructions when they say to put jack stands under the mufflers. With two people, one person will hold the muffler while the other works on the insulator. Liberally drench the insulator with WD-40; this will make it somewhat easier to get off, but this hanger has the same hangup as the tailpipe hanger. Work it free in the same manner as the tailpipe. We also wedged a screwdriver between the insulator and the bulkhead so that both people would have their hands free to yank the muffler around.

Here are the flanges. Ford made it nice -n- easy to install a cat-back system. Don't lose the bolts -- you need them.

Watch out! That stock muffler is heavy. In fact, we weighed it -- they're 15 pounds apiece (the Flowmasters are about 8 pounds each). Try not to let them land on your noggin.

Assembly is reverse of disassembly.

Ha ha! Just kidding. Pay close attention here; this is where the package instructions really get hazy.

Check the flanges for fit by sliding them over the flange studs. One of ours wasn't drilled right. If you have this problem, a few minutes with a rat-tail file should do the trick. Too bad we didn't realize ours was messed up until after we were trying to install the whole pipe/muffler assembly!

Slide the flanges onto the inlet pipes. The flat side of the flange goes toward the catalytic converter. Then slide the mufflers onto the pipes. The bends in the inlet pipes should face down, not to the outside as indicated by the diagram. Do not install the exhaust clamps yet. Set the pipe/muffler units aside.

Look at how the original hanger is on the muffler and faces one way...

...while the new one is welded to the clamp and faces the opposite!

Take the new muffler hangers and have a look at them. Unlike the stock arrangement, these ones are welded to an exhaust bolt rather than to the mufflers themselves. Also, unlike the provided diagram, the new hangers are installed in the reverse direction from the originals. You'll know you've got it wrong if the muffler tries to smash into the driveshaft.

The easiest way to install these is to, again, ignore the instructions and liberally douse the insulators with WD-40. The hangers slide in reasonably easily if you prelube them, and don't have mufflers attached yet.

Take the inlet/muffler assemblies and slide them over the flange studs, turning as necessary to get the most clearance from the body. Hold off on the nuts for now. While one person holds the muffler, the other fastens the muffler hanger to the outlet pipe. Do not tighten this clamp yet.

Now it's time to snake the new tailpipes through the suspension. With the car supported by its axle, you can't do it. Really. With the car supported by the body, the axle drops on your face. Not good either. Our solution? Leave the car sitting on its jack stands, but use a floor jack to lift the body of the car a couple of inches. Do not lif the car off the jack stands! The idea is to generate a little more clearance. It worked great for us -- the pipes slid right in.

With the body still lifted, slide the tailpipes into the muffler outlets. It shouldn't be too hard.

Check for interference between the tailpipes and the body/chassis. You don't want anything getting squished when you lower the body. In particular, make sure the top of the pipe bend is aligned nicely within its well.

Carefully lower the body back down.

Now you need to put the tailpipe hanger into the insulator. This takes a bit of effort. First, lube the insulator with WD-40, then yank it over as far toward the outside of the car as you can. With a lot of pushing and pulling, the hanger will slide into the insulator. Keep trying. It will.

All that's left to do is align and tighten. Start with the flange nuts; tighten them up really well. Doing so will change the clearance substantially between the tailpipes and the bumper. Someone should stand behind the car throughout this phase to ensure equal positioning.

Install and tighten the exhaust clamps for the inlet-pipe-to-muffler connection. Sometimes the muffler may want to slip or twist; it's important to have a spotter keep an eye on the rear alignment. Rotating the muffler just a fraction of an inch has noticeable effect in the rear. Patience is very important here.

Tighten the muffler-to-tailpipe exhaust clamps. As before, keep an eye out for tailpipe alignment. This is also the time to check the tailpipes for interference; there are a couple of places where the suspension and chassis come very close to the pipes, but they shouldn't touch.

Go back and tighten everything again. By this point, it should all be tight enough that nothing moves.

Tighten it again.

Have someone else check to make sure everything is tight.

Got the idea?

You are done! Lower the car and clean up your mess. Wait'll you start it for the first time! What a sound.

Ahhh... much better!

Wow, what a change. The Mustang GT now sounds more like the (essentially unmuffled) Paradise Garage Charger. But it's more in tone than volume; sure, it's louder, but the main thing is that it sounds more authoritative. Anyone who tells you the American Thunder exhaust is too noisy is either a wuss or is your mom. Most of the volume comes on around 2000 rpm; the rest of the time it's quite civilized.

On these computerized cars, you may wonder what the computer thinks of all this. Well, the best thing to do is give it amnesia. Unplug the computer (make sure all the electrons drain out) and the 'puter forgets all about your old, quiet, muffled exhaust! When you bring your computer back on line, it'll need to be driven around normally a little bit to relearn its settings. You don't have to do this; it just takes longer for the computer to adjust if you don't.