I did a search but didn't really find what I was looking for. I've got a pair of Flowmaster 40 series Delta Flow mufflers laying on the shelf. I'm thinking about putting them on my Crew Cab. How loud, monotonous, or droning is the sound at highway speed? One truck I had you couldn't here them at speed, but my Ranger has a constant drone to it at highway speed. I have a 5.4 and the rear is geared 3.55. My RPMs usually stay around 1700-2000 RPMs at highway speed depending on what speed I am going.

 

I just put some on my truck, same motor and gears. Not sure if they are 40 series, but I can barely hear them at highway speeds.

 

my super44 only drones on the highway when towing or climbing, and it isnt a really loud drone.

 

I can barely notice my 40 at highway speeds, however there is a good drone at about 35-40, and again around 60, once I clear 65 though it's smooth sailing.