a search would lead me to believe that many of yalls have changed out the cats on their f150. This week im doing the plugs and coils (if need be) on my 04, and Im going to get ready to order cats and a cat-back exhaust should one or both of the cats be plugged.

as I see it, replacing both cats on both sides looks like a royal pain. The way to go would be a preassembled set, but I cant find any for my truck (according to fordparts.com I have the 4R75W tranny) that I know of.

so what are the ins and outs? do I need to replace both cats on each side, or is one more likely to plug? Is it easier in the log haul to weld in universal cats? is it all steel or stainless? (I can only weld straight steel at my shop :P)

and also if anyone knows the walker/magnaflow or whatever part number to fit my truck that would be sweet I think I found the eastern p/n but its iffy for a SCAB fit... 30458 and 30459

truck is a 2004 F150 FX4 SCAB with the 4R75W (the 100k mile disposable tranny lol) thanks in advance guys

 

i doubt the cats are plugged if you dont have a ton of miles on the truck. ive seen vehicles with 200k miles with the oem cats working just fine. but if youre set on changing them i would just go to an exhaust shop and have them do it and go ahead and build you a true dual exhaust for the same price or cheaper than what you can buy a catback system for. i bought a cheap-o catback system w/ Flowmaster SIDO 2.25" and it sounds good. but my buddy that had a 2.5" true dual with two SISO Flowmasters sounds WAY throatier

 

truck has 136k miles on it. I know the exhaust leaks like swiss cheese, so thats probably going to go anyway...

for whats wrong with my truck its either plugs, coils, or cats... so with as long as its been misfiring im sure the cats have taken SOME abuse

 

I am in the same boat as you. I plan on ordering my new cats sometime in the next week. I have 2 super 44 flowmasters SI/SO and it sounds great, but it just isnt loud enough. Dont order the whole catback exhaust, or you will be spending more than you need to.

 

Some say go with high flow cats to get a deeper tone, myself unless they are plugged/clogged I don't know why they need to be changed. The factory flow is sufficient for a normally aspirated engine in our trucks. My .02
Good luck

 

X2 on the oem cats. The reason some (not all) have changed cats is for sound purposes, but if you do it will cost you a couple hundred. Don't purchase a catback do it your self, buy a muffler of your choice (listen to youtube video's) and have a muffler shop configure the exhaust the way you want it. It will be cheaper. Don't get too big with the exhaust piping because you will loose some low end torque. 3" max for siso, 2 1/2 max for sido or siso duals might keep a little more torque with 2 1/4 trues duals.
pm sent

 

well, I have a pit i can use, so the labor isnt hard, as long as its a drop in exhaust. was going to just use 2.5" SISO. Not so much for tone or volume, as much as having a leak-free exhaust. For the same money as an OEM replacement from a local parts house I can do a gibson or magnaflow SISO that will bolt in, which is the only reason im even considering a new exhaust. not saying a grumble wouldnt be nice Its very possible I will be able to weld the leaky joints together and not have to replace the exhaust at all, just the cats. And thats IF the cats are bad.

My fear is that the money involved (wife and I are buying a house) will accumulate rampantly having an exhaust shop do my cats by the time im done buying parts.

 

These kits, as good as they are, are never "drop in". There's always wiggling, heating, and cutting to get them in. You're already at a huge avantage with the pit though. The clamps used by the factory make it darn near impossible to remove the clamps and pull off the pipes by sections, especially if your at home, crawled up under the truck (on jackstands).
By the time I've bought the good kit, removed the old stock exhaust, then lined everything new up, clamped it all down, it would have been cheaper (including my "free" labor) to have it done at my local privately owned muffler shop.

 

Lots of sites that will give you the numbers you will need. I worked in the auto repair industry and welding never really fixed a leaky, older exhaust. Aluminized steel is your cheapest option, and having an independent muffler shop (oh god not midas) do it will be the cheapest. Napa sells dynaflow/dynamax, walker systems a direct oem fit. Pricey though. I know you are on a budget, shop.

 

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