How to Install Flowmaster American Thunder Cat-Back Exhaust - Split Side/Rear Exit on your F-150

Removal:

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 exhaust isolators as well as the two front flange bolts. This will make the removal and installation process much easier.

3) Support the muffler with a stand and remove the two bolts at the front flange connection. Now, with the help of an assistant, slide the exhaust system to the rear to disengage the hangers on the exhaust from the rubber mounts on the vehicle. 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).

Installation:

1) Mount the left rear tailpipe hanger bracket #226HA to the frame on the driver’s side of the vehicle. Place the included 3/8 x 3.50” bolt thru the 226HA hanger and into the hole indicated in the photo. On the inside of the frame, place the HA226 back-up plate over the bolt followed by a flat washer, lock washer and nut. Using two 9/16” wrenches tighten firmly (Do not over tighten).

2) 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:

141” WB - Regular Cab / 8’ Bed - Trim 4” off of inlet pipe #26532S (do not use #26277S)
145” WB – SuperCrew / 5.5’ Bed - Use inlet pipe #26532S with no modifications (do not use #26277S)
145” WB – SuperCab / 6.5’ Bed - Use inlet pipe #26532S with no modifications (do not use #26277S)
157” WB – SuperCrew /6.5’ Bed - Trim 6” off of extension pipe #26277S and use with inlet pipe #26532S
163” WB – SuperCab / 8’ Bed - Use inlet pipe #26532S and extension pipe #26277S with no modifications.

3) Place the inlet pipe onto the back of the existing OEM head pipe and fasten using the 3/8” x 2.00” bolts, nuts and washers provided in the hardware kit. Tighten just enough to hold in place, but still allow for adjustment.

4) Slide the inlet hanger #490HA over the back of the inlet pipe and insert the hanger into the factory rubber mount. Do not tighten this clamp yet. If required, place the extension pipe #26277S onto the back of the inlet pipe. Then place the inlet of the muffler onto the back of inlet pipe and support with a stand. Level the muffler and tighten the clamp at the inlet enough to hold, but still allow for adjustment.

5) Install a provided clamp onto each of the muffler outlets. Then place the right side tailpipe #86327S into position over the axle and into the right side muffler outlet while also connecting the hanger on the pipe to the rubber mount on the vehicle. Tighten the band clamp enough to hold, but still allow for adjustment.

6) Place the front section of the left side tailpipe #86323S into the left side muffler outlet and insert the hanger welded to the pipe into the rubber mount on the vehicle. Tighten the clamp enough to hold, but still allow for adjustment.

7) Place a clamp onto the expanded end of the left rear tailpipe section #86324S, slip rubber hanger #HA168 onto the hanger of the pipe. Place the expanded end of the pipe over the back of the front section and connect the rubber hanger to the frame mount installed in Step 1. Tighten the clamp enough to hold, but still allow for adjustment.

8) Slide either the side exit pipe #86325S or rear exit pipe #86326S onto the ends of both over axle pipes. Place a clamp onto these slip-fit connections and tighten just enough to hold in position. Place the two stainless tips #ST461 onto the exit pipes and tighten the pinch bolts just enough to hold in position. Rotate the exit pipe and tip to the desired distance from the fender or bumper so that the tips are in the desired location. The final adjustment of the tips is best left to the final step, with the vehicle on the ground so that you can get a good view.

9) Now go back and adjust the position of all 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, you may now securely tighten all clamps, including the front hanger/clamp assembly.

10) After the system is secure, slide the 7/16” hanger keeper onto the left tailpipe hangers. This keeper will prevent the hanger rods from slipping out of the rubber mount.