Hey guys got a question I'm sure this is already been asked before, but the rear cat on my driver side of my, 97 f150 4x4 with a 4.6 is rattling the noise drives me nuts! You can only hear it when you first take off at around 25 mph and when you start to slow down to come to a stop! Ik it has four cats but can I go to just 2 cats without hurting to much? And as inexpensive as possible! I don't live in California also I don't live in a state where we do emissions testing! But I prefer not to gut them either! Also don't really want to spend a butt load of money on factory ones either? Any help would be greatly appreciated! Thanks a bunch folks

 

The bad news is, you have an engine management system that has multiple o2 sensors as well as multiple cats, and even though you may not have inspections in your state, but it's a federal law and that means anyone from local/sate law enforcement, to a state air quality control member, fish & game officer, can cite & impound the vehicle...…. you have no say in the matter but you do get to go to court, sit and listen to judge decides if the vehicle should be scrapped or repaired and if its returned to you, you get the great opportunity to now have to visit a federal referee station......and when you go to sell it someday, you guessed it, the federal referee station also get to give your smog inspection cert for the sale..... and BTW, you still get to pay for all the repairs, court costs, impound fess, etc.
dropping the rear cats will also cause another issue with the downstream O2 sensors in that they are now likely too far away from the cats to get accurate readings...… and defeating those is not smart either as the oem software has "modeling" within in..... meaning it doesn't just say if x is this then I need to do Y, its really pushing into understanding & responding and as such, it will make erroneous conclusions that can cause some real damage to the engine...such as messing with the air/fuel mixture that will over time cause "valve tuliping"...….it's just a lot cheaper to replace the cats.

 

Yeah that figures I was just wanting to replace the rear cats remove the front I wish I would have known this before I bought it? I don't mean that I didn't know it was federal law to remove them or gutting them is illeagal to do, or anything I should've did some more research on having 4 cats and that they haven't made a good after market ones that actually take the place of 4 or whatever! This is why I truly prefer to drive something newer than a 72! But buying one restored can cost a lot also! But whatever if I have to I will just deal with the noise I guess! At least for now! Thanks for the info

 

Is it possible to do one side both of them? Then do the other like a month apart? I know that may sound dumb but I'm on a fixed income and is hard for me to spend even that much money in one whack! But I will figure out something I guess and is it possible to buy the 2 separate ones front and rear in the aftermarket and just have them cut out and welded in by a muffler shop? Although I noticed that it is kind of hard to weld them in with the exhaust bolted to the manifold! Thanks again for the info!

 

Are you sure it's the cat and not the cats heat-shield that's loose and rattling? The shields weld sometimes rust away and require a large stainless hose clamp to hold the two halves together.

 

Yeah I've tried that then drove it but I think not positive it's just the right rear is rattling but not a 100% . positive it's just that one🤔

 

Yeah I've tried that then drove it but I think not positive it's just the right rear is rattling but not a 100% . positive it's just that one🤔 I was really hoping that was it on the loose heat shield but no luck on that sorry I posted twice!

 

just wanted to give an update it turned out it was the dust shield behind the driver side front tire the bolt was a little loose at the top tighten it up no more rattle didn't have to spend any money or got the catalytic converter or tear off the heat shield thanks again guys

 

that's great news !!!!!!!!!

 

Yeah because if I would have tore off the heat shields and it would have still rattled or wasted hundreds of dollars for new cats and it still rattled! I wouldn't have been a happy camper lol! So no money spent and no rattle what a relief!!! Thanks for the info! I've been trying to figure out the rattle for over a month lol!