Exhaust help please!

I have an 01 Limited lifted with a hitch.

I want to replace from before the cat and back. So basically cat and cat back exhaust. I have never done this before and I am not a welder but I am noticing some things that don't look right to me.

My cat has the flanges on both sides of it.
Where my exhaust meets the cat there is a flange on it before the muffler.

All these aftermarket cat back systems don't seem to have the flange on the front of them to meet up with the cat. It looks like Rusty's and Magnaflows all seem to be the same way. The Borla looks like it has the flange but some people have said they had to modify it to make it fit on a lifted jeep.

Rustys says: "* 01 models require cutting of muffler flange. Cut on the muffler side of the flange where muffler is welded, about 2.5" behind flange. Then slide the flowmaster onto the 2.5" extension."
So it seems to me like the Magna flow is the same way as Rustys from pictures.
I don't want to leave a old crappy piece of pipe there that is going to rust out faster than my new exhaust and once that piece holding on the new exhaust goes to hell, then what? My exhaust will no longer be connected to the cat.

Since I am replacing the cat, should I be looking for a cat without the flanges? Then how do I connect the cat to the muffler and also in the front to the downpipe? Since the downpipe has a flange on it also for connecting the cat to it. I do know that my cat doesn't have an 02 sensor on it either.

Any help, part numbers, pipe size info or pictures would be greatly appreciated!!!:wow:

Thanks!!

You should weld the new system together. You can install new exhaust pipe with clamps, but it:
1) looks like crap.
2) may leak around the clamped pipe.
3) will rust out at the clamp unless well protected.
4) be impossible to pull apart. The pipes deform/crush around the clamp.

If you can't weld, call around to small local exhaust shops. Ask your friends who have had work done. Ask street rodders. See a nice custom car around, ask the owner. We jeepers forget that the other automotive guys have to have the same mech. work done. They just don't need 8" of up travel. A local shop will do installs on systems like the ones you listed for $50.00- $100.00. As long as you're not asking them to pull the cat out, they won't care. Don't go to sears, monroe, etc. In my experience, the chain shops will rip you a new one.

If you find a shop to do your work, ask them how much they can get your system for. Or even ask how much they will bend one up and slap it on for you. A "cat back" system is a muffler and tail pipe. I had that made for my CJ for under $80.00 a couple years ago. If you have a local shop buy your system for you, it might cost a little more, but a reputable shop will stand behind their work. After all, you break the outlet out of a really expensive muffler, You can't mail you jeep back for warrenty work.

As for the old crappy pipe flange: Where did your system let go? Most of the time, the factory system looses the muffler, or the tail pipe where it kicks up over the rear axle. If there's no holes in the cat. to muf. pipe, I'd bet that peice of pipe will outlast your new system unless the new one is stainless. (side note: twisted up my '00 XJ and the exh. started leaking' It was a flange seal that let go. Sounded like crap but the system was sound.)

Install: Most of the time, a new cat is welded into the existing system without changing anything else, or it is welded onto the down pipe and a new muff/tailpipe is clamped to the back of it. If you are going to off-road the jeep, install some kind of flex joint between the cat and muffler, and add an extra pipe hanger close to the joint. Your muffler will last a LOT longer.

All this is written assuming you NEED a new exhaust. If you just WANT an new exhaust for a different tone, precieved preformance gain, etc, Then all the crap about making it, well, ignore that.

Last note: if you get a non-stainless system, clean the oil off the pipes and paint them with hi-temp/engine paint. They'll last about 3 times as long.

I know the flanges you're speaking of, and Dynomax is one for sure that comes with it. I have a '96, which doesn't have a flange on the downpipe, but just to be safe they sent me one to attach to the cat if needed. Needless to say it's sitting in the garage. From the cat back, you shouldn't need a flange - either weld it or clamp it together. I assume Flowmaster, Magnaflow, and other mfgs have probably also taken this into account, and should send you a downpipe-to-cat flange, but just to be safe, ask for one when ordering. The flange that connects the cat to the muffler is unnecessary. If you're ordering a new cat and a new muffler, just clamp or weld, hang it in the rear, and be on your way. Hope this helps.

I am actually looking to replace the exhaust because the muffler is starting to leak so I figured I would just do a cat back. Then I started thinking about doing a cat back and also replacing the cat with a high flow one.

tbburg, My factory cat has flanges on both sides so they just usually hack all that out and weld in a new cat? As for stainless or aluminum, I live in Wisconsin so the weather has me leaning twords stainless, however aluminum is a lot cheaper. Maybe I will call around and see how much they will charge if I bring in a new cat and cat back to see what they will charge to weld it all up.

So should I order all the suff without the flanges and then take it to a shop. I am just wondering what sizes I should get though? Such as cat in and out sizes.

Thanks for all the help guys!!

OK So I called MagnaFlow directly to ask what parts I would need to purchase from them to replace my cat and also a cat back exhaust. I was explaining to the guy about the flanges and he was telling me that I was wrong and there are not any flanges. We argued for a while and I said fine, ignore the flanges what parts would I need if I scrapped everything from the downpipe back and he said well we don't do custom work and that their pipes would butt-fit and would have to be welded, end of call.

So guys/gals help me out here what sizes of pipe etc do I need to make this work? I drew up the picture above to give you an idea of what my factory setup looks like, which I guess is different than most XJ's??

Do I cut off the flange on the Downpipe and attach/weld a pipe to that. Then what size pipes am I looking for the letters? The guy at magnaflow told me that their pipes but fitted and they had to be welded, arent they supposed to slide into one another and then get clamped or welded? Also If I have all this stuff welded together then there isn't any flex which would be bad too, right?

What should I do guys??

Thanks and sorry if I ramble but I have never dealt with anything like this. I have just put a cat back on before on another car.

klennop I would suggest just replacing the muffler with a good flowing aftermarket one, and leaving the rest alone. The pipe on the 00/01's is the same size (like 2 1/4 or 2 1/2 I can't remember for sure) as what usually comes in a cat back system, and the CAT is actually quite free flowing as it is. When I replaced the muffler on my 00 I put on a Flowmaster 40 series on it, and it made a nice seat of the pants difference. It really woke up the part, and full throttle jaunts. I'm not saying the full cat back is the wrong thing to do. Just that I think it's not needed on the later models, and you could save some money by just replacing the most restrictive part.

scoobyxj said:

klennop I would suggest just replacing the muffler with a good flowing aftermarket one, and leaving the rest alone.

Click to expand...

That seems like the easy thing to do with the exception of leaving the little snub "D" to attach the new cat back to. It would make more sense to me to cut out both of the flanges between the cat and muffler and attach the new cat back to "C".

I just ordered the flowmaster 50 from Rusty's and I am thinking I can just put another piece of pipe in between the muffler and the cat to get rid of the flanges all together. That would be OK, correct?

The flanges are not necessary at all. They make a place the factory can split the pipe so repalcing 1/2 the pipe without welding. Having the flanges can help you if you need to get under there and work on something. Ever try to muscle a complete system in or out from under a car? Even on a lift it's a pain!

The flowmaster has a good rep. People seem to like them. I have no direct experience with them.

Pipes can be butt-welded together, or 1 pipe expanded over the mouth of the other and lap-welded. Makes little difference in the strength of the weld. If you do the slip fit and lap-weld(or clamp) the down stream pipe should be the one expanded, and the mouth of the up stream pipe should be de-burred to get the best performance.

I myself like the flanges. They are a little more complex/expensive to install in the first place, and they do make a place for a leak(seal failure) but when you go to work on something, and that stupid rusty pipe is in the way, and the choices are a big hammer and broken manifold studs, or a sawzall, those bolt up flanges are a godsend.

If you're mostly driving on the street/light trail, keeping it mostly stock; doesn't matter. If you're thinking about future modifications, crawl under your jeep and look at the tail pipe in relation to the transfer case/transmission/front-/rear drive shafts/gas tank/shift linkages/etc.