2nd Gen Non-Engine/Transmission cyclic droning noise

[shendren]

when the truck is idling and i walk past the exhaust, i can hear a cyclic, droning noise. what could this be? can't pin it down, but it is worse sometimes more than others. maybe a hot cold thing. ???

 

[Steve Campbell]

Could it be....

something coming apart inside the muffler or cat?

 

[shendren]

could be the muffler? the cat is missing... .

 

[illflem]

Not positive without hearing it firsthand but almost every 12 valve whose cat I've removed (for efficiency verification) has made a cycling drone at idle afterwards. I think the stock exhaust is tuned to be as quiet as possible, altering/removing even one component changes the sound.

 

[ToolManTimTaylor]

And Bill, You would never dream of doing such a thing now would ya unless it was an experiment (BTW you are only 44 posts away from 10,000 in your history) #ad




I agree with illflem tho. the exhaust is a funny thing. I played arround with mine (First ditched resonator i. e CAT , shortened the pipe , did the straight piped thang in both 3" and 4") and the best I have now in terms of noise at idle came from the HX40 being it is 4" from the start (Not a 3"flange swagged to 4"). I noticed that same drone with my old banks exhaust and when I changed over to full 4" it dissapeared. Why... . IDUNNO but if I were to guess it was that 3" turbo outlet causing resonance.