Engine/Transmission (1998.5 - 2002) Unusual exhaust brake sound

[plongson]

After installing the new 4" exhaust I now have a very unusual "SWOOSH"ing sound or like a loud "SHHHHHH" when I apply the exhaust brake. This only happens when the truck has slowed down or if the brake is applied at a low RPM. Very unusual... it never sounded like this with the factory 3" exhaust. It appears to work just fine, but it has me puzzled as to what would cause this strange sound all of a sudden...

 

[GFrance]

Your 3" exhaust was just too restrictive to hear the exhaust brake before. The air leaking fast out of a tire sound is normal exhaust brake sound.

 

[nps]

I've got a 3 inch exhaust and hear the 'leaking tire' just fine.



You actually hear the noise all the time, but until the RPMs drop enough, the sound of the retarding engine overpowers it.



What muffler were you running on the 3 inch exhaust? Now on the 4"? My guess is that it's the difference in mufflers causing your new found swoosh.

 

[plongson]

It is just a straight through "Diamond Eye" muffler... and stock was just all stock. Let me tell you, when they say a "straight through" system, they mean it... there are damn few bends or kinks. It seems to have improved the EGT's, but this truck runs so good anyway, it is hard to tell if there is a performance improvement. EGT is really what I was chasing after, seems I caught it. It is definatly louder though... I hope not too much so. Guess time will tell. .



Thanks guys...

 

[nps]

Yeah, mine is a straight through Flowmaster. The stock muffler was the culprit in masking the sound before.