Yesterday I replaced all my catalytic converters with a bolt-in MagnaFlow OEM/Federal kit (MagnaFlow Part #49690). I was hoping it was truly bolt-in because I'd never done any exhaust work. I did the swap in my garage with basic hand tools and only needed to ask my neighbor if he had something I needed on two occasions.
Here's the MagnaFlow kit in the box:
View attachment 422699
I did like
@mrblaine suggested to someone else on the forum and drove the Jeep up on ramps. I would be using the only shop jack I have to hold up the transmission. Having the space under the Jeep to roll around on a creeper and work, without jack stands in the way, was great. I took out both lower O2 sensors and set them aside on my workbench for later installation into the new kit.
View attachment 422700
To help me remove the skid plate I set jack stands on one side of the skid, so it could rest there while I worked on the other side. Once both sides were free I used my knees to pop the skid free of the stands and slowly lowered it to the floor. I did have a nice surprise when I took off the skid plate. The bolts looked pretty amazing for their age. (Thank the maker for vehicles that lived most of their life in the Southwest.)
View attachment 422701
The skid had some surface rust where it makes frame contact. This was the first instance where I asked a neighbor for something; in this case a wire wheel/cup. He set me up with an angle grinder and wire cup. I knocked the scale off both skid and frame, and applied a few coats of primer and satin spray. I let all of it dry as I continued on with the exhaust work.
View attachment 422702
I used a regular 15mm socket and several wobble extensions to remove the old pre-cat bolts. Once the old cats were out, it was easy to see why the Jeep was having problems.
View attachment 422704
Here's a closeup of each pre-cat.
Bank 1 Pre-cat:
View attachment 422705
Bank 2 Pre-cat:
View attachment 422706
The media in the Bank 2 pre-cat was loose and sideways at the bottom of the cylinder. Not cool.
For comparison, here's a look at the Magnaflow internals.
View attachment 422707
I put the replacement pieces together just to eyeball that they would fit. At the top of the picture you can barely see the shop jack which held the transmission and a jack stand was used to support the muffler's front pipe.
View attachment 422708
I replaced the old metal clips at the manifold with four new Mopar clips. The old ones popped off using a flat screwdriver. I looked over the old bolts and found one had wear on its threading; meaning its threads were not as deep as the other three. I know one of those four bolts/clips was very loose (it was the front bolt/clip on Bank 2) when I started removal. I can't be sure the worn bolt was that particular one because all the bolts dropped to the floor as I went I didn't immediately inspect them. I figured since I was using new clips I'd not reuse the bolts. I ran to O'Reilly's for some M10-1.5 x 50mm bolts and ended up with flanged bolts.
Installation was a bit more tedious. For it's part, the MagnaFlow stuff fit just as described. This was the easiest part, honestly. Direct bolt up to the OEM muffler, and the hanger was where it needed to be. The four bolts at the pre-cats started relatively easy by hand, but the real work came when I needed to tighten up everything at the pre-cats.
The space between the bolt head and the pre-cat top is tight. The top of the replacement precat may also have a slightly different angle than the original. All I know is, the setup I'd used to remove the old bolts wouldn't work with the new bolts. No socket and wobble extension combo worked. My 15mm wrench was too long to work in there. This was the second time I needed to go to my neighbor. Luckily he had a 15mm crows foot and a stubby open-ended 15mm/14mm combo wrench. He saved me from a major delay that another trip to O'Reilly's or Harbor Freight would have added to this project.
To get those four bolts tight, I went back and forth between the stubby 15mm and the crows foot for what seemed like
forever. I just kept turning, flipping the wrench, turn some more; or crank on the crows foot, rotate the wrench and go again. I got everything as tight as I could, I have no idea how I'd honestly torque those bolts. Underneath the vehicle I made sure I had at least an inch clearance between the pipes and the oil pan, the front driveshaft, and the transmission bracket.
I reinstalled both post-cat O2 sensors and started the engine. No loud exhaust, no rattles. I checked the voltages on the sensors. Both sensor 1s were reading similarly, and both sensor 2s mirrored each other. This looked to be an improvement from the wildly varying bank 2/sensor 2 voltages before this swap. (But really, let's be honest, the media was shot, so yeah.)
Driver's Side:
View attachment 422710
Passenger Side:
View attachment 422711
I then took the Jeep for a quick trip. It is noticeably different. It has no more exhaust note than before, but its obvious how the catalytic problems restricted the engine's performance. I didn't notice any vibrations idling or driving and didn't hear any rattling/impact noises over bumps.
Since replacing the fuel pump two weeks ago and now this swap, I notice a major difference in the Jeep. Part of me wonders if it the fuel pump was failing and damaging the pre-cats when I took ownership. Being that the Jeep came to me used, and was my only sample of how a TJ drove, I assumed it drove how it did because that's just how they are.
Final Thoughts:
I'm going to buy a set of metric and SAE stubby wrenches and (at least) a set of metric crows foot wrenches. I plan on giving everything a few heating/cooling cycles then I'll check bolt tightness and I will need something to get up in there. A flex-head, ratcheting, closed-end wrench or a flex-socket (a
really shallow one) might work, but I'm going to go with what I know works for now. This one was expensive, to be sure, but if I have lengthened the life of the Jeep, I'm happy I had the time/ability to do this work.
I've had mine for a little over a year now. Still quieter than my Bestop was.
