I have cut out my cat and replaced it with an 18" magnaflow. the rest of the system is a 6" bully dog catback with a 6" turn out. i love the big rig sound outside. But the drone at hwy speeds and when pulling isn't so cool. I've read just about all the posts about eliminating drone. I'm not sure what to do...will probably go with a nelson, but my question is what is the source of the drone? Correct me if i'm wrong ...but i believe it is vibration of the exhaust system at a specific frequency that is transfered into the cab. I was wondering if anyone else had any input on the subject. I believe that if the exhaust was insulated in some mannor it wouldnt cause any drone. What about wraping the cab section of the exhaust with header tape or something equivalent??? Any suggestions would be appreciated.

 

I basically have the same thing but I still have the Cat on. I was thinking of adding a section of flex pipe in place of the Cat(for off road use only ) to seperate the Exhuast from the engine a little. I don't know about most big trucks but all the cars I work on have some kind of flex section or coupling that allows some engine movement independent of the exhaust.

 

I've read that some guys have clamped a section of angle iron to the front pipe to stop or reduce the drone. Some one else said they did something to the rear pipe over the axle. I don't remember what.

 

I tried the angle iron clamped in different locations and I still have the drone. I don’t personally mind it so much but because of the family, I don’t care for the amount of noise it produces in the cab. When I get on it, my one kid asks if I’m speeding. I wish I could get rid of it (the drone not the kid) .

 

someone told me that you need a 8" diameter straight through muffler and that should eliminate the droning. Also one of my friends put a 24v ats exhaust manifold on and that helped some, but that would take a lot of extra work.

 

We have seen good results reducing drone using our Exhaust Guide installed directly on the down pipe under the passengers feet. The idea is to redirct the exhaust down the straight part of the pipe under the cab and reduce the turbulence. You can see pictures on this page right under the tips http://www.dieselpowerproducts.com/exhaust

 

I dont doubt that the exhaust guides will work...but i doubt they will allow for the deap throaty sound i want my truck to have on the outside. They also look very restrictive???? check out my pics of my exhaust in my gallery.
I think my tip extends far enough past the body to keep it from causing the drone.
I have ordered some header wrap to try to absorb some of the vibration.
I also found this product and think i am going to give it a try also.
http://www.epiflex.com/epi_flex.html

Anybody ever try this? Any thoughts?

 

I don`t think the drone is from movement of the exhaust system as much as it is actually caused from resonance within the system. The larger the pipe, the more resonance you will have. A good way to get rid of some of it would be to add a layer of sound deadener to the floor board of your truck. This would be alot of work, but it would make a differance. I`ve work around big stereo`s for yrs, and the thoery is the same, you mass load the suface to reduce vibration. Also, the header tape should reduce some of this as well because, again, you are mass loading the exhaust pipe, therefore reducing the resonance eminating from the pipe. Just my .02