I need to replace the right side cats. The substrate rattles if I smack it and I get a chirping noise on accel. It was tossing the below threshold code until I shimmed out the rear o2 to get me by until I had time to pull the cats. I can sawsall out the old one to make that easier, but does anyone know if the trans crossmember must come out? Looks like the skidplate must come out....anyone do this before? 2002 Fx4 5.4 extended cab short box....4r70w tranny....Thanks!

 

I just drop whatever is in the way and unbolt the pipe assembly at the exhaust manifolds.

On my 97 and 2000 F150s after removing the pipes I made three equidistant scribe marks where I was going to cut to make sure I would "clock" the parts together correctly I Sawzalled out the cat shells, finished removing the ceramic with a hand sledge and a hunk of rebar, MIGed them back in place and reinstalled. Might not be theoretically perfect but has worked flawlessly for years. I used resistors to eliminate the rear O2 sensors. I chopped off the connectors from the old sensors and soldered them there so I didn't disturb the stock harness (and benchwork is more comfortable).

All hardware gets anti-seize before reinstallation. Total cost, a Sawzall blade, some MIG wire (fluxcore is fine too) and some anti-seize. Runs indistinguishably from stock tho a bit louder.

I used a Jegs downpipe on a Chevy whose cats had been stolen and it fit nicely. (It got a PCM reflash so I had a rear 02 sensor delete.) I don't know if they or Pacesetter make a full downpipe for the F150 though.

Of course these are offroad only vehicles never to be used on a highway yadda yadda.

 

Yeah...I looked under it today. The skid plate needs to come off and I see no way to get that out with that crossmember in the way. I did the RH manifold this summer so that connection will come right off. I'll probably need to loosen the left converter at the manifold to get that stud nut assembly off that holds the rh side. Then sawsall out the two connections shy of the actual connection, pull the assembly out, then work on getting those leftover stubs out.