Owners manual

SYSTEM #527504
1996-1999 CHEVROLET GMC
5.7L HD & 7.4L TRUCKS & SUBURBANS
NOTE: This muffler is not a bolt on unit. The removal and installation of this muffler requires
cutting, welding and tube bending equipment. If you do not have the proper tools or skills, we strongly
recommend having your new Flowmaster installed by a professional muffler shop. The following
steps will assist you when removing/installing at home.
12/14/09
Removal:
1) Raise the vehicle and support securely with jackstands.
2) On Suburbans and Standard Cab/Long Bed trucks, remove the oxygen sensor located directly
ahead of the muffler. Other applications do not require this step.
3) Support the stock muffler with a jackstand. Mark and cut the inlet pipes ahead of the muffler
as shown in the diagram on the following page. Then, using a sawsall or cutting torch, cut the tailpipe
off just behind the muffler outlet. Remove both the tailpipe and muffler from the vehicle. Use extreme
caution whenever using a torch.
Installation:
1) Position the Flowmaster muffler onto the inlet pipes. Using a stand or support of some type,
level the muffler front-to-back. (Note: The muffler will sit slightly rotated.) Check that the cat pipe has
not dropped, and that it is not making contact with the cross member. Once properly positioned, fully
weld both inlet pipe connections.
2) On Suburbans and Standard Cab/Long Bed trucks, remove and discard the plug that is located
in the bung located on the right side muffler inlet, and install the oxygen sensor in its place. On all
other applications the plug should be left in place and checked for tightness.
3) From this point on the tailpipes will need to be fabricated as desired. Be sure to properly and
securely hang the exhaust system, utilizing factory mounts/positions whenever possible.
Note: Due to the proximity of the oxygen sensor, it is mandatory that the all slip-fit
connections be fully welded.
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