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How to Install a Flowmaster American Thunder Catback Exhaust on Your 1998 Mustang GT & Cobra

Installation Time

2 hours

American Muscle
Shop Parts in this Guide



1. Raise the vehicle up on a hoist or rack to working height. If you do not have access to a hoist or rack raise the vehicle and support securely with jack stands.

2. Separate the steel tailpipe hangers from the rubber mounts at the rear of each tailpipe. A lubricant may ease removal.

3. Using a hacksaw or sawsall, cut the stock tailpipes off approximately 2” behind the muffler case.

4. Remove the stock tailpipes from the vehicle and set aside.

5. Support the stock mufflers with a stand. Separate the steel muffler hangers on the rear of each muffler from the rubber mounts on the vehicle.

6. Remove the two nuts at the muffler to catalytic converter connection.

7. Remove the stock mufflers from the vehicle.


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

2. Position muffler#942548-183on the right side of the car in the stock location. Install the nuts at the front of the flange connection. Connect the hanger rod to the rubber mount at the rear of the muffler.

3. Slip tailpipe#16169into the muffler outlet over the rear axle. Slide the tailpipe hanger rod into the stock rubber hanger before inserting the pipe into the muffler outlet. Install a 2 1/2" clamp and tighten enough to hold, but still allow for adjustment.

4. Repeat these steps on the left side of the vehicle using muffler #942548-182 and tailpipe#16170.

5. Adjust and align the position of all the pipes to provide a satisfactory fit. Maintain at least 3/4”clearance around the new FLOWMASTER Exhaust System, the drivetrain and all chassis components. Also keep suspension travel in mind.

6. After the hangers are adjusted to their final position, place the provided hanger keepers on the two muffler hangers. This will keep the hangers from slipping out of the rubber mounts.

7. For a cleaner appearance and more secure installation, we highly recommend welding all slipfit connections. If you live in a geographical area that has harsh winters or sees a great deal of precipitation, the use of high temperature paint over the welded areas can help to prevent surface rust and premature corrosion.

Packing List

QtyDescriptionPart #
1Muffler, Left942548-182
1Muffler, Right942548-183
1Tailpipe, Left16170
1Tailpipe, Right16169
1Parts KitPK301
22 1/2” ClampMC250S
27/16” Hanger Keepers

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