I had the 4040XL which is a resonated muffler. It sounded really nice until I towed with it and than it had terrible drone.

 

Did you have the stock resonator in place?

Under load my 4040xl is heard, cruising is quiet. I haven't towed with it yet but I'm thinking it'll be noticeable.

 

Only Mega's have a resonator.

 

ok. So it's a cat eh? I've seen the terms used both ways so not sure myself.


Ahem, when I installed my 4040xl I left the stock big round thing after the turbo but before the muffler in place

 

Yep thats a cat. The resonator on the mega is post-muffler and in the tailpipe itself.

 

Have to agree the 4040XL without a cat is much louder than stock and almost unbearable while towing. I put my stock muffler and cat back on for now due to having close neighbors and having to leave for work at 4:45AM.

 

The Donaldson 40" and the mega-cab resonator is about as hi-flow as you can go and zero drone, its quiet with a good tone, and when your really on it is sounds awesome. Easily passes the neighbor/wife test.. yet keeps the truck breathing and sounding healthy.

 

I packed the chambers in my 51" nelson with fiberglass and wrapped the outside with more fg and covered with more sheetmetal and it was as guiet as stock and had a deep tone outside. Then I changed the turbo and it got loud again and droned. I put a 4" cherrybomb ahead of the muffler and it's plenty good enough to talk in the cab again. Craig