I’m wanting to replace my factory muffler on a 2010 F-150 5.4 triton I’m reading that the factory exhaust is 2.75 but the only sizes I’m seeing with Flowmaster are 2.50 or 3” which should I go with

 

Not sure about 2010 but my '14 had 2.75 in and 3" tail pipe. Had the exhaust shop cut off the factory resonator and weld in a 3" Vibrant Ultra Quiet performance resonator to the stock flange and added a 3" SI/SO 18" body Magnaflow (12249). He cut the stock tailpipe right after the muffler and welded on a short connecting piece to slip in the muffler, all in stainless. Got the Magnaflow as a open box special on Amazon. Resonator also from Amazon.

 

I believe factory for your truck is 2.5" in and 2.75" out. Couplings will be required for either one you get, and I'm not sure if the 2.5" coming from the engine will fit into the 2.5" with or without a coupling.

If you are getting a shorter muffler, you will need extra pipe as well.

Is an exhaust shop doing this or you? If an exhaust shop is then definitely don't worry about either one as they will both work fine.

 

Thanks for the help guys!! And I’ll be doing the job myself