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How To Install Flowmaster American Thunder Axle-Back Exhaust on your 2005-2010 (GT, GT500) Mustang

Installation Time

1 hours

Tools Required
  • 13mm, 15mm socket
American Muscle
Shop Parts in this Guide

Installation diagram for:

SYSTEM #817410

2005-2010 FORD MUSTANG V-8



1) Use a 15mm socket to loosen the nuts on the clamped connection between the mufflers and the over-axle pipe. Then use a 13mm socket to remove the bolts that secure the muffler hangers to the frame of the vehicle. There are two hangers on each side of the vehicle. These hangers must be removed to allow removal of the stock mufflers. After taking the hangers down, slide the muffler off of the over axle pipe and set the muffler aside. Take the hanger mounts off of the stock muffler and put them onto the Flowmaster mufflers.


1) 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.

2) Place one of the supplied #MC250BS clamps onto the inlet pipe of the right muffler #852566-R. Slide the muffler onto the over-axle pipe, support with a stand. Place the hanger mounts back into position on the frame and reinstall the factory bolts. A 13mm open end wrench will be needed to reach the bolts above the muffler. Level the muffler and tighten the clamp on the muffler inlet enough to hold but still allow for adjustment. Repeat the step for the left muffler.

3) Adjust the position of the mufflers to provide a satisfactory fit. A minimum of รณ clearance around all parts of the system must be maintained; while keeping suspension travel and vibration in mind. After adjustments have been made, securely tighten all clamps.


Due to variance in the factory H-pipe location you may need to adjust the H-pipe by loosening the two front factory clamps (at the H-pipe) and the two clamps at the muffler thus giving you the ability to achieve satisfactory fit and placement of the Flowmaster mufflers and placement of the tips in the factory cut-outs.

4) 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 a high-temp paint over the welded areas can help to prevent surface rust.

Technical Support (707) 544-4761

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