The muffler that's best for the 4.0 is going to depend on how free-flowing you make the exhaust.
If you're just doing a muffler swap and keeping the rest of the exhaust stock, a Super 40 or 44 might sound OK.
If you are doing a complete exhaust with a high flow converter and 2.5" mandrel bent tailpipe, those mufflers are overly loud and a bit "ricey" sounding on the 4.0. Not to mention that they also have a lot of drone and resonance.
In the end it depends on your goals and your budget. If you just want better sound than a muffler swap is A-OK. But if you want more power you really need to not only replace the muffler and tailpipe, but also the converter as it is a large restriction.
Originally Posted by cherokeen
Been quoted cheaply for a 2.5" catback installed but i do want something with a good sound. I was going to consider a flowmaster 44 but undecided, is there much price difference and much power/sound difference between a flowmaster 44 and just a catback?