TJ Exhaust on a YJ
(97 Jeep Wrangler 4.0L collector pipe & CAT
installed on a 94 Jeep Wrangler 4.0L header)

Vehicle Information: 1994 Jeep Wrangler, manual transmission, 4WD, 4.0L I6 cylinder, 85,000 miles.
These are basic information on how my husband and I installed a 1997 Jeep Wrangler 4.0L exhaust collector pipe on our 94 Wrangler. Use this information AT YOUR OWN RISK!
PLEASE NOTE : This write-up is for REFERENCE ONLY. The parts you buy and the vehicle you own will ultimately determine exactly how you complete this modification. Not all Wranglers are the same year to year - and you may discover your vehicle can and might be different than mine.

Why change the stock exhaust??: On the older Jeep Wranglers (95 and older - YJ's) the exhaust is routed underneath the transmission and is vulnerable while offroading. I have an engine skid plate under my Jeep - which has protected the exhaust and engine for at least 4 years, however.... the clearance in between the exhaust and the engine skid was about 1/4" or less. During certain offroad situations - I'd land on the engine skid causing it to bend upward causing the exhaust to rest directly on the engine skid plate. For many years - I'd remove the engine skid plate and have it straightened (park a vehicle on it) and put it back on again (gain about 1/8" clearance between the engine skid and exhaust). I got tired of removing the engine skid after each trip. Putting the TJ exhaust on will eliminate this problem because the exhaust routes in front of the oil pan and never crosses underneath the transmission.

Without Engine Skid plate - stock YJ exhaust
before - no skid

With Engine Skid Plate - stock YJ exhaust
before - with skid

 


Parts Research: I spent some time researching my options of ordering parts - calling Auto Stores and junkyards. The Auto stores told me, "That's a dealer only item - I can't get them here" and the junkyards aren't allowed to sell used catalytic converters and were against cutting it off and selling the part without it. I could've tried harder and searched more - but I decided to call up a good friend of mine who works at the dealership. He hooked me up with a new 97 Jeep Wrangler 4.0L collector pipe - including a new catalytic converter (attached as one unit) & hardware for a very good price. Thanks Scott!!! Below is a picture of the stock 97 TJ 4.0L collector pipe with catalytic converter (LEFT) And the stock 94 YJ 4.0L collector pipe with catalytic converter (RIGHT)

TJ Collector Pipe too short to reach Muffler & Second O2 sensor bung

While the collector pipe was still in place during our TEST fit - we discovered the pipe was just a bit too short and didn't reach the muffler. I went to a local exhaust shop and requested a piece of pipe 6" long with 2.25" inner diameter on the pipe end and 2.5" inner diameter on the muffler end.

After installing this extension piece, we were able to tighten down the exhaust at the header and get a clearer idea of how things look.

(BELOW) - You can clearly see the extension piece we've added to mate up to the muffler. On the left of the extension piece, you can see the second O2 sensor bung. I had a spare O2 sensor that I used to plug the hole temporarily until I find the proper sized pipe plug to fit.

Clearance Issues

After installing the extension piece - we noticed the entire exhaust was sitting about 2" lower than the original set-up. The new catalytic converter is more rounded and larger than the original. It was resting directly on the transfer case cross member. Not good....

To remedy this - we went back to the exhaust shop and had them bend a custom piece of pipe with a 2" elevation (2.25" inner diameter on both ends). The piece ended up being approximately 18" in length total. We had to cut about 12" out of the TJ collector pipe to fit this elevation pipe in. Installed this just prior to the transfer case cross member.

(TOP Picture below) - the elevation pipe installed.

(Bottom Picture below) - Clearance after the elevation pipe was installed. Take notice to the finalized exhaust hanger in the right of the picture.

Final Inspection & Completion

After the elevation pipe was installed - we tightened everything down enough for a test with the motor running. We cranked the engine over and everything was fine!!

FINAL Pictures

Picture from front -
without engine Skid plate
(immediately after installation)
Picture of oil pan -
without engine Skid plate
(immediately after installation)
Picture of the transmission - with engine Skid plate
(picture taken after some road & trail miles)
Picture of the front -
with engine Skid plate
(picture taken after some road & trail miles)
Picture of the side -
with engine Skid plate
(picture taken after some road & trail miles)