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How to Install Flowmaster American Thunder Stainless Steel Cat-Back Exhaust - Single Side Exit on your F-150

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) Begin by applying a lubricant to each of the rubber hanger mounts, as well as the clamp and flange bolts. This will make the removal and installation process much easier.

3) Remove the two bolts at the front flange connection, and loosen the band clamp connection that is behind it on the inlet pipe. There is a locking pin at this joint, to separate it you will have to slide the muffler assembly back a little bit, twist the front inlet pipe clockwise, and then you can slip the front inlet pipe back to remove.

4) Now you can slide the muffler tailpipe assembly to the rear to disengage the rubber hanger mounts that support it. Once free, the assembly can be removed by working it forward over the rear axle. (If you are working on the ground it may be easier to cut the tailpipe off at the rear of the muffler to simplify removal)


1) Based on production variations, this is a list of cab designs, bed lengths and wheel bases that outlines the requirements for the front inlet pipe. Please follow the instructions for your particular wheelbase listed below. Double check all measurements before cutting your inlet pipe:

126 Regular Cab/6.5’ Bed - Trim 20” off the inlet pipe #26276S (do not use #26277S)
133 SuperCab/5.5’ Bed - Trim 14” off the inlet pipe #26276S (do not use #26277S)
145 SuperCrew/5.5’ Bed - Trim 2” off the inlet pipe #26276S (do not use #26277S)
145 Regular Cab/8’ Bed- Trim 2” off the inlet pipe #26276S (do not use #26277S)
145 SuperCab /6.5’ Bed- Trim 2” off the inlet pipe #26276S (do not use #26277S)
157 SuperCrew /6.5’ Bed - Trim 8” off the extension pipe #26277S and use with inlet pipe #26276S
163 SuperCab /8’ Bed- Trim 2” off the extension pipe #26277S and use with inlet pipe #26276S

2) Place the inlet pipe onto the back of the existing OEM head pipe and fasten using the nuts, bolts and washers provided in the hardware kit. Tighten just enough to hold in place, but still allow for adjustment. The S-shaped pipe will be offset toward the frame of the vehicle.

3) Slide clamp hanger #382HA over the back of the inlet pipe and insert the hanger into the factory rubber mount. Do not tighten this clamp yet. If the extension pipe is used, use the provided 3” band clamp at the connection between the inlet and extension pipe.

4) Place the inlet of muffler #8530570-262 thru the #382HA clamp hanger and onto the inlet pipe, support with a stand. Level the muffler and tighten the clamp just enough to hold in position, while still allowing for adjustment.

5) Slide a 3.50” clamp onto the muffler outlet neck. Place tailpipe #36047S into position over the axle and insert the hanger at the front and rear of the pipe into the rubber mounts on the vehicle and slide into the muffler outlet. Tighten the clamp just enough to hold, while still allowing for adjustment.

6) Adjust the position of all the pipes and muffler to provide a satisfactory fit. A minimum of 3/4” 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 and install the 2 7/16” hanger keepers onto the hanger rods.

7) For a more secure installation, we recommend welding all slip-fit connections.


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