View Full Version : PORC SYE for XJ, TJ, other NP231 applications

October 24th, 2005, 04:00 AM
I recently finished the installation of a Performance Off-Road Center (PORC) Slip-Yoke Eliminator for my 1996 XJ Cherokee. The SYE is an essential upgrade to the NP231 t-case as it removes the built-in slipyoke that can cause damage from vibrations and fluid loss if the shaft is damaged and has to be removed.

On 1996 and later XJs and the '97+ TJ Wrangler, the design of the NP231 allows the rear driveshaft to be removed without losing fluid when driven, but the changed design also makes it much more prone to vibrations due to the greater unsupported length of the tailshaft.

The PORC SYE eliminates the weak point of the slipyoke and also beefs up the output of the t-case by using a mainshaft that is much thicker than stock along with a yoke-style output that allows the driver to run a front-style driveshaft in the rear. In my application, a stock front shaft is the proper length to fit the rear, and the design allows me to bolt the driveshaft up quickly and easily with only four Grade 8 bolts.


Assembly can be done on the vehicle although space might be restricted. I chose to install mine on the workbench as I was also removing my transmission to fix a broken bellhousing. See your FSM for proper removal methods.

I'll leave assembly and disassembly out of this writeup although they are covered in more detail at http://www.yuccaman.com/jeep/porc_sye.html and in the well-written assembly instructions that came with the kit.

Be advised that the mode ring snapring supplied with the PORC SYE does not always fit properly. It may need to be lightly sanded to reduce the thickness, or the stock snapring may have to be used. In my case, I was able to get the mode ring back in place using the stock snapring so care should be taken during disassembly to avoid ruining stock parts.

The obligatory mainshaft comparison pics: http://www.yuccaman.com/jeep/pics/mainshaft.jpg

PORC is above, while the stock output shaft is in the middle with a stock YJ shaft on the bottom. The red line denotes the mode ring snapring location.

I have run across a few instances where the rear output seal as supplied by PORC will leak shortly after installation. I don't know if this is due to the seal being improperly lubricated prior to running it or if it's a manufaturing defect. Just be aware of it and make sure you lubricate it early and often.

Final Notes: After reinstalling the transmission and t-case, I am finally able to drive I-25 without feeling as though I'm driving a paint mixer - the vibrations from the bellhousing and the rear RE driveshaft were so bad that any speed over 20mph caused the interior to shake and vibrate so strongly that it was next to impossible to see behind me.

I am running a stock 4.0L automatic front driveshaft in the rear, and strength doesn't seem to be an issue with that driveshaft yet. The bolt I pulled out of my '96 speedometer holddown was a 5/16"-18 but that wouldn't fit in the new PORC housing. I picked up an M8x1.25x16 bolt at ACE and it fits perfectly. Apparently PORC uses metric fittings but there's nothing in the instructions mentioning this. I can easily see some unsuspecting soul ruining a good tailhousing because they forced an SAE bolt into a similarly-sized metric hole.

On a final note, the PORC SYE appears that it is made in Taiwan if this is a concern to any potential buyers. I would definitely recommend this SYE for Jeepers interested in a stronger SYE with easy installation.

October 26th, 2005, 12:33 PM
Put one in my YJ, and the pinion seal leaked after less than 100 miles, and I too had an issue with the snap ring. Otherwise its a great deal, and the quaility seems to be fine.

July 29th, 2006, 01:27 PM
No problems with mine yet, and im at I think 200 miles

August 2nd, 2006, 06:42 AM
I have no problems with mine after about 10,000 miles. :)

August 2nd, 2006, 06:52 AM
Ive got the same one in my XJ...i do notice that my output seal has the ever so slightest leak like alot have complained about...but its not anywhere near fast enough to warrent fixing it. Ive got probably 3000 miles on mine and it works great so far!

August 2nd, 2006, 05:15 PM
Funny thing that you mention the output leak...I was just under the Heep this weekend, grumbling about the leakage. It's minor, it doesn't really effect anything, but dammitall it bothers me that with only a few thousand miles on it, I have leaks from the SYE. The leaks from 200,000-mile old parts are to be expected...

August 2nd, 2006, 08:59 PM
Mine doesnt even really drip...just enough to dribble and gunk up everything with dirt underneith. For 170 bucks, im not complaining though...

January 12th, 2007, 08:25 AM
Have the same kit on my TJ worked great and a good price @ $180/delivered. Had a stock front drive shaft cut down for my CV rear ($65) no more vibes with 4" of lift.