Flowmaster AMERICAN THUNDER 817725 Service manual

409S®Stainless Steel
02/18/15
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).
Pg 1 of 4 Technical Support [phone]
Installation Instructions for:
SYSTEM #817725
2015 FORD F-150 TRUCK
2.7L, 3.5L & 5.0L ENGINE
Does not fit Standard Cab – 6.5’ Bed

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 #86327Sinto 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.
Pg 2 of 4 Technical Support [phone]

8) Slide either the side exit pipe #86325Sor rear exit pipe #86326Sonto 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.
PACKING LIST
Qty Description Part#
1 Inlet Pipe 26532S
1 Adapter Pipe 26277S
1 Muffler 8530452-176
1 Right Tailpipe 86327S
1 Left Tailpipe, Front 86323S
1 Left Tailpipe, Rear 86324S
2 Side Exit Pipes 86325S
2 Rear Exit Pipes 86326S
2 Stainless Tip ST461
1 Parts Kit PK800
1 Ring Clamp Hanger 490HA
1 Frame Hanger, Rear 226HA
5 2 1/2” Band Clamp MC250BS
2 3” Band Clamp MC300BS
1 Rubber Hanger HA168
1 Back-up plate HA226
2 7/16” Hanger Keeper HW502
1 3/8” x 3.50” Tap Bolt HW234
2 3/8” x 2” Bolt HW211
4 3/8” Flat Washer HW303
3 3/8” Nut HW103
3 3/8” Lock Washer HW309
Pg 3 of 4 Technical Support [phone]

Technical Su
pp
ort
(
707
)
544-4761
Installation diagram for:
SYSTEM #817725
2015 FORD F-150 TRUCKS
2.7L, 3.5L & 5.0L ENGINE
Does not fit Standard Cab – 6.5’ Bed
409S ® Stainless Steel