LocknRoll

Getting set to replace the exhaust on my 03 4.0. Rusted way bad, from manifold to tip...multiple leaks. Can't complain I guess...all stock and the old gal has spent her life driving on NS and NB salt roads. 10 years is probably all one can expect.

Already bought the Dynomax cat back kit(19391), researching the front part now. When I search for an 03, I keep getting results for a 2 piece Cat system(downpipe with minicats and a bolt on rear cat). My 03 has a 1 piece system which seems to be the same as the 04 parts.

Example: Searching BOSAL for my 03 shows 079-3108(Y-pipe plus mini cats) + 079-3107(rear cat). But mine looks like the BOSAL part for an 04, 079-3140( 1 piece y-pipe with mini cats plus rear cat).

Anyone else done this job...Maybe Canadian Jeeps had the 04 exhaust in 03?

cheers
lnr

oldfart

You might have an 04 jeep but it was first registered in 03.

salad

Typically the one model year begins production partway through the previous calendar. My 1999 XJ was built in summer of '98 and first registered then. What's your VIN say?

LocknRoll

Thx for the replies,,,rig is an 03. Build date was Nov-2012, VIN says 03 model year, original sales receipt from dealership says 03.

I've sent emails to the CAT manf's seeking clarification...my hunch is that most 03's were sold in the US where the rear cat was "optional" depending on the state..

Raises the question I guess...can we run with just the mini-cats and a straight pipe where the rear cat is? Would still have all 4 O2 sensors, so I'm guessing it would run fine. Legal?

cheers

oldfart

Depends on where the o2 sensors are. The sensors before the cats help the computer set the fuel mixture, the sensors after the cats monitor the performance of the cats.

salad

Probably not, it's a violation of federal law to remove any factory-installed emissions equipment. No idea what the rules are on this site regarding discussion of such. The exhaust system with the 4 O2 sensors shouldn't notice if you cut the whole exhaust away at the down pipe but I wouldn't recommend it for the sake of legal compliance and the health of the guy driving behind you. The mini-cats aren't really that effective compared to the big 'un.

ArgoGirb

I just replaced front pipe/cats with magnaflow from just jeeps,it has a 3 bolt flange at end,had to cut orig.pipe.I too have the 3rd cat,build sheet says low emission vehicle(put enough cats on anything can be low emission lol)I also thinking of removing the 3rd one,no sensors around it. https://www.justjeeps.com/product.ph...0&cat=0&page=1

LocknRoll

Thx for the additional replies folks.

I ended up just buying the 2 piece replacement system from Walker. Perfect fit, now have a quiet Jeep again. On to the next fix, my rusting hinges...seems there's always something the old gal needs... lol.