I know have the rattling cat problem. I'm going to pull the heat shields to see if that works first. It only rattles at about 1500 RPM's I'd guess, and then it goes away, but man it sure is annoying!

Isn't that what the problem was? The heat shield?

 

i think thats what it is dude. mine only does it at idle, when the engine goes it either gets covered up by the engine/exhuast noise, or just doesnt rattle.

It gets a little worse, every day. Started sometime shortly after i put on my flowmaster. One day, i'll hack them and throw in some hi-flows.

 

That's what I believe I'm gonna do. I looked at them for a little while today, and I don't think it's the heat shield. It's not rattling at all when I'm underneath.

 

Probably your converter brick in pieces rattling in the housing, that's what mine was.

 

You mean broke in pieces? That could be it...it sure is annoying man. Anyone know of some REALLY cheap high-flows?

 

Yep, I still have the pieces, I saved them for proof that I was not crazy. My driver's side broke up, the first one, and rattled like crazy. I think Motorhaven has some that are the cheapest I've seen so far. Remember, one high flow replaces two stock cats.

 

i think in CA, you need to replace all 4.
But when i do it, i'll only use 2.

also, try eBay, for CATCO cats. usually a little over half the price of magnaflows

 

I have 15K miles on my truck and my cats rattle. They've been rattling for 5K now. I've gotten used to it. It sounds bad but it's a Ford problem. What-r-ya-gonna-do? NOTHIN'

I got used to the noise and it doesnt bother me anymore. eventually, the sound has got to go away.

Tom

 

Yup, I'm getting used to it myself, but I guess some el-cheapo high flows would be good to have. They wouldn't really give me anything performancewise, but the sound gone alone would be worth it.

 

i think going from 4 cats to 2 "hi-flows" would free up some restriction and give some top-end....

and it'll get a buttload louder

 

reducing the restriction will free up some upper end, but will sacrifice torque no doubt.

me

 

here's what the future holds for rman's truck (in no particular order, no time limit):

hi flows
headers
efans
chips
salsa
cam

performance-wise, at least

my 13's and hydraulics, complete with dancing bed, come in today

 

I had the same issue with my 1999 F-150 with the rattling broken cats. I had Ford replace both sides twice! Finally I am out of warrany now and my drivers is doing it again. I have gone to www.cheapexhaust.com and found them both for a total of $500! I have though that of switching it but I run straight 3" exhaust from the cats back (no muffler) so that would be really loud. Without the muffler it sounds great but I do have neighbors to think about.
For BUSA01- You only have 15K on your truck! When it is making the noise pull into a Ford dealer and let them hear it. I work at a dealership as a service advisor and if you can display the issue they cannot ignore it. Get it covers for free as long as you can!

 

Yea, but I have a 40 series flowmaster with only 18k miles on it. Won't the Flowmaster void that exhaust warrantee?

 

Having flowmasters from the Cats back has NO EFFECT on your warranty! I work at a BMW Dealer and I cannot void a warranty unless you have disconnected your O2 sensors or modified the manifolds in some odd way. There is a FEDERAL LAW stating all emission contol items (catalytic converters) are covered by manufacture warranty for 8 years/80000 miles. I just replace two cats on a 1998 740il with 78500 miles and they weren't as loud as the ones on my truck.

So, if all you have done is put mufflers on you have done nothing to void your warranty. I had my second set installed with a cat back Roush Racing system on mine.

Good luck

Smokey