Exhaust Upgrade: Dynomax Super Turbo Muffler & Magnaflow Catalytic Converter

41+ pictures! The biggest write up yet!!  ◆◆◇◇  Medium


Dynomax MufflerAs far as I know, Chrysler/Jeep is required to replace your malfunctioning exhaust system until 8 year/80,000 miles on the Jeep even with your 3year/36K warranty. With my luck after hitting 88,xxx miles, my catalytic converter has gone bad that it was rattling like "you know what."



Jeep Old Exhuast System RemovedI heard many asking about bad catalytic converters and how to come about diagnosing if they are good or bad.  Most answers were, you would know if you have one that is going bad.  To add to that answer, you would know because it rattles.



Magnaflow Catalytic Converter PackagingAfter researching for the parts, I have found that you can purchase a factory replacement Magnafloww catalytic convert from eBay for the 1/3 of the dealer price.  I purchased the Magnafloww cat for $80 shipped to my door from ebay vendor called "performance-curve".  At first I thought I was only buying the cat but it actually came with the down pipe as well.  This made the box huge.  Initially, when I got the box, I had no idea what came in the box.  I was wondering why they would use such a big box to contain the Magnafloww cat.  I even thought they have sent the wrong item.


Magnaflow Catalytic Converter ContentsIn the packaging, I found the Magnafloww cat, a band clamp, downpipe, and a paperwork that you need to sign (keep as a record) stating that you are not removing your old cat and you are replacing it because it is malfunctioning.  According to the document provided, it is illegal to remove and reinstall if the factory equipped catalytic converter is operating correctly.


Stock Old MufflerRusted U ClampI ordered the Magnafloww catalytic convert, but later found out it is extremely hard to separate the stock cat from the muffler.  This is due to the U clamp that factory used to hold the cat and the muffler together; it creates creases on pipes from the cat and the muffler.  Over time with constant heat and rust basically forms around the crease, literally fusing those two pieces together.  Knowing that I will be working on my garage floor, I won't have much room for me to move around or use a long prybar.  I decided to just to ditch the stock system and upgrade the muffler as well.  So I don't have to wrestle the exhaust system.  


PreFormed Band ClampTo prevent the crease forming on the new system, I decided to get band clamps that are preformed around two different sizes of pipe.  It fit perfect around the connection and allowed very easy adjustment after the install.  The post install adjustment would be almost impossible if you welded or used U clamps to install.


Another search began for cat-back systems for Jeep TJ Wrangler but I have not found any write up on the exhaust upgrade for TJs.  I only found many saying how they like their systems and how their exhaust systems are performing.  That didn't help much with the install. There is nothing to compare different systems on the market.  However after searching for a while, I found a few clips of the exhaust note of different system.  Even so, I couldn't tell how loud they were.  


After reading various articles/thread available online, I decided NOT to go with Banks and Borla.  One of the reasons is  that they are just plain out overpriced.  A muffler and a piece of pipe made of stainless steel did not justiy $300 price tag.  Also, I read many describing they sound farty and pretty loud.  They did come with the limited lifetime warranty yet, there were other brands that also came with the lifetime warranty for less than a half of their price.


Dynomax Muffler PackagingDynomax Cat Back Muffler InstalledThen I came across a few people saying the Dynomax Super Turbo bolt on cat-back system is only tad louder than stock system.  As I wasn't insterested in purchasing louder system but rather a stock replacement at a reasonable price, I made the decision to go with the Dynomax.  It was only $134 shipped from Summitracing.com. Once again, I was surprised by the size of the box the Dynomax came in.  The new cat-back components are nice and shiny.  They are aluminumized components.



1. You need to cut some components to replicate my procedure.

2. You are working with large and heavy parts which is ackward to handle under the vehicle.  Second set of hands is required for proper removal and adjustment during installation.


Tools & Parts Needed

Socket Set

O2 Sensor Removal Socket (Optional if you have a big monkey wrench)

Floor Jack and Jack Stands(4)

Dynomax Cat-Back System (~$130 from SummitRacing.com)

Magnaflow Catalytic Converter Part# 23227 for 1997-1999 (~$80 from eBay)

Preformed Band Clamps (qty. 2, 2.5" radius)

Saw (Metal Cutting)


Job Hours

4 hours





Jack Stand Location1. Park the Jeep securely.  Disconnect negative battery cable.  Make the jack stand as tall as you can so that it can be placed under the transmission as shown.





Floor Jack Position2. Remove the transfer case skidplate. Click on the picture on the left to link to a procedure on how to remove the t-case skid plate.






Transfercase Support Bracket3. Remove the transmission support bracket from the transmission. You don't need to remove the transfercase mount.






Support Old Exhaust System Prior to Removal4. Place the jack stands right under the old exhaust system plumbing.







O2 Sensor ConnectorO2 Sensor Back Location5. Disconnect the O2 sensors.







Removing Down Pipe6. Disconnect the down pipe from the exhaust header.







Rear HangerHanger7. Remove the two exhaust hangers from the frame.  I had to grind the body tub to remove the bolt completely, as shown in the picture.  Be careful as the exhaust system is now free to fall.  Clear away.  Hopefully carefully placed jack stands on step 4 will catch the fall.





Where to cutCut8. To remove the old exhaust system, you will have to make a cut on the tail pipe near the muffler.  YOU WILL NOT BE SAVING any of the old exhaust system except for the oxygen sensors and the hangers if you are following this instruction.  After the cut you will have to twist and turn the tail section of the cut, to remove the old tail pipe. I also cut the hangers from the pipe to save the rubber insulation.


Oxygen Sensor InstalledFront O2 sensor installed9. Remove the old oxygen sensors and install them into the new system.







10. Install the down pipe on the header but do not tighten the bolts down yet.  Just tighten it enough to keep it on.  Place the other end of the down pipe on the jack stand.






11. Place the band clamp provided with the Magnaflow catalytic converter on the down pipe.


Cat PreFit12. Slide the Magnaflow catalytic convert into the installed down pipe.  Put the band clamp and tighten it snuggly.  Place another jack stand underneath the muffler to hold it in place.





13. Reinstall the transmission support bracket on the transmission.  Make sure the cat support is installed through the bracket.



14. Install the muffler using the band clamp.  Tighten the clamp enough to hold the muffler in place.  Move the jack stand from the cat to the muffler.





Tail Pipe15. Route the tail pipe into place and install the band clamp between the muffler and the tail pipe.






Rear Hanger Install16. Hang the tail pipe. Install the exhaust hangers to the frame.  Do it in the order as described.





17. You should be able to remove all the jack stand now.  Connect oxygen sensors. Reinstall the skid plate.


18. Tighten the down pipe to the header.  Adjust the muffler and the cat so that it will clear the skid plate and the rear shock.  If you don't do this right you will hear rattling when the engine is running.  Tighten all the band clamps.


Completed19. You are done!







Additional Pictures of the Install


Magnaflow Catalytic ConverterInstall CompletedClamp 





Old vs. NewCutUnistallationGrind Point 





O2 sensor removedDownPipeOld Exhaust System 












The Verdict


Overall, the sound is louder than I expected.  Maybe this is because of the Magnaflow catalytic converter.  It definitely has a bit more rumble than stock and around 2500 RPM, it gets dramatically louder.  I guess this is where the system got "Turbo" in its name.  I do notice the quiet rumble like V8 when idling.  I really like that initial rpm spike when you start the engine and the sound caused by it. Jeep definitely sounds a lot more aggressive when I step on the skinny pedal but unlike the idle it is not that distinct V8 sound.  It is more of a unique sound like no other exhaust systems that I have heard in deeper than ricers, but not as deep as V8.


After the install, my jeep went from 14-15 MPG to 16-17 MPG.  I used to get around 210-230 miles per tank but now I am getting around 250 miles before the fuel warning light.  That is like getting another extra gallon or two. In other words,  it is like saving a gallon or two every tank.  I also noticed that I am not on the skinny pedal as much as I used to be.  I guess that can be translated as increase in power.  Not the power you would notice but enough to save gas.


Am I pleased with the install?  You bet.  Increase in the MPG alone will pay for itself very soon considering near $3/gallon gas price.  What is better than mod that pays for itself?!


After driving for about 500 miles the exhaust started rattling again.  This happened because the clamps were not on tight.  After readjusting and reclamping, the rattle was gone.  Now I got over 1000 miles on the system with no rattle.  If the rattle comes back again.  I will readjust the clamp and add some thread lock to it.


If you have any questions or recommendations, please let me know!!



I tried my best to document as much as possible along with pictures.  I hope you find them useful. However, do use the information provided here "as-is".  Daily or the author does not warrant or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, or process disclosed.  Use the information at your own risk.


Written by Michael on 6.10.2006.