I have a question for you all. I swapped the american thunder flowmaster catback that I had on my 99 SS to my 94 Z28. I had a custom 2.5 ory made for it at the same time with the flowmaster y collector. My problem is there is a rattle in the car only at certain rpms under moderate accleration. Usually happens around 1800-2500 rpms. Is this just a characteristic of the 80 seires muffler on a LT1 car? It would sound awesome if it wasn't for that. The car is an automatic by the way. Any suggestions on what it could be? I have removed the sheet metal heat insulator on the passenger side of the car where the cat was. Would I be better off to go with a single 3" 40 series flowmaster in place of this setup and have like a custom 1 or 2 out on the left setup?

 

when i first read this i thought you had a dual setup but after i saw he 80 series flowmaster part i caught on, but it still may be possible you're having the same rattle i do with my duals because they run through the factory spot, and that rattle is coming from where it goes over the axle, only noticeable from inside the car, but mine only does it at a dead idle and usually only while its idling really low in gear. good luck and i hope that helps (if it is the same rattle location as mine its just the pipes hitting the heat shield above the pipe havent found a good fix yet but im workin on it...)

 

My exhaust rattle was caused by a failed cat. The inside material was in chunks and would rattle around. To find out bang on the exhaust near the cat and see if it rattles inside. Good luck.

 

check the one spot where the y pipe hooks onto your catback right around there, there is like a metal brace thing that bolts to the chasis (sp?) your exhaust runs over top that and when the guy custom made your y pipe it may have lowered the exhaust or something so when your cars starts to get high in the rpms it is rubbing agaisnt that or something

 

cat1055man: The car has no cat on it, I had it removed with we did the exhaust.
lt1zpwr: Are you talking about that brace that is on the tailshaft of the tranny? I'll post up some pics for you. These are the only two views i have as of now, I'll get some more tomorrow.
flowmaster y
catback

 

the best way to find the noise is to get under the car and move the exhaust around until you find it. you might not even have to get under it. try to move the exhaust tips around and see if you can generate the rattle. have someone shake the tips around while you listen and you should be able to find the general area that way. or you could run the engine to make the noise and try and pinpoint it. my exhaust started rattling just yesterday, I lightly stepped on the tips a few times and got an idea of where it was, reached underneath and found that I have a loose heat shield.

BTW AZ2NV, do you go to Clemson University? if so, how is the engineering dept down there? I heard Clemson was building a pretty big engineering building? later!

Jeremy