JB-Conversions Super Short SYE

NWJeepn.com Product Review
JB-Conversions HD Super Short Slip Yoke Eliminator kit When being short really counts! Article by Ed Holnagel
The Problem: It’s common knowledge amongst most Jeepers that when you install a lift of 3 ” or more on a Wrangler, the short rear drive shaft is dropped to an angle that will produce unwanted and harmful driveline vibrations. Driveline vibrations besides being just plain annoying can lead to other serious problems. Pinion seal failures, excess wear on the u-joints and in the case of one of our own staffers, a split T-case on the highway at 60 mph. Trust me it isn't a position you want to be in. The reason for this problem is a shortcoming in the original design of the NP231 transfer case in that the output shaft has the slip joint in it rather than the drive shaft (unlike the front drive shaft). The rear drive shaft is fixed in length and thus the "slip yoke" moves in and out with the flex of the suspension. This type of "slip yoke" setup forces the use of a very short rear drive shaft and leaves little or no room for the angle changes caused by lifting the Jeep. The Fix:
There are two common methods for solving excessive driveline angles after installing a lift. The cheapest and easiest way is a center skid plate lowering kit. This kit is a set of six spacers that lower the center skid and because the transmission and T-case are supported by the skid it lowers the angle of the driveline and places it back to near factory angles. To our way of thinking there is a big difference in doing something “right” and doing something “cheap”. The two terms in most cases just do not mix. And in most of our experience doing something “cheap” will just cost you more money in the long run. However it just does not make any sense to me to lift your Jeep for better clearance and then lessen the break over clearance by lowering the center skid. If you choose to install a long arm lift or a lift of over about 4" then lowering the center skid is just not an option. Don't think however that if you own a Chrokee that you are imune to this problem. Even though the longer cousin of the Wranlger has a longer rear driveshaft they can and do at times still suffer from driveline vibrations caused by excessive lift. The “right” way of fixing the problem is the installation of a Slip Yoke Eliminator kit in the transfer case.
Choosing the right SYE kit: It defies explanation when someone will drop upwards of $3000 for a good lift kit for their Jeep and then balk at $300 for an SYE kit. As I stated above there is “cheap” and there is “right”. On the cheap end of the spectrum is the "hack and tap" kit, usually priced at around $100 or less, which requires you to cut the output shaft of your T-case, drill and tap a hole in the end of it and then re-install the yoke. While this will allow you a longer drive shaft it is far from the best solution. Good SYE kits run from about $250 to around $350 and there are many to choose from. That is why the JB Conversions Heavy Duty Super Short SYE at around $299 retail is not only a veritable bargain in SYE kits but as we will show the superior choice for your Jeep. You have spent a lot of time an money building up your rig, why go cheap when it comes to the SYE? About JB Conversions: JB Conversions has been producing SYE kits for the YJ and TJ since 1994 and has built a solid reputation for excellent engineering and quality. Of all the kits they have sold they have never had a failure! With the latest trend in Jeep suspensions moving to long arm designs such as the Rock Krawler lifts we have installed on 2 of our Jeeps now, JB Conversions has answered the need for an even shorter SYE to help get the best performance out of your suspension. The longer the rear drive shaft the better no matter what suspension you decide to choose. The newest offering from JB, shortens the overall length of the NP231 by another 3-1/8” over the standard HD SYE. This may not seem like a big number but when it comes to Jeep drive shafts, 3" makes a big difference. After exhaustive research of the many SYE kits on the market we came to the conclusion that the Super Short SYE was the best kit on the market for the money, performance and for the following reasons:
JB Conversions nickel plates their parts inside and out in much the same way that a lot of aircraft quality parts are manufactured for increased durability and added protection. The output yoke has additional clearance for those of us needing a high angle driveshaft and is shorter than any of the competitions yokes. If you are installing a long arm lift with gobs of articulation then trust me you really want this! The output shaft is a proven 32 spline design for added strength. The mechanical speedometer sensor has been replaced with an electronic speed sensor and custom tone wheel. Therefore the speed sensor is recognized by the Jeep speedometer as stock resulting in a smooth and reliable operation. JB-Conversions has a great reputation for quality and customer support.
Notice the difference in length between the JB shaft (top) and the factory output shaft (bottom)
With the Super Short SYE installed, driveshaft lengths can exceed 22"! A huge improvement over stock and much better than any other SYE on the market.
As you can see by the two transfer cases at right, the JB-Conversions kit is much shorter that the SYE of the competition allowing for greater driveshaft length. Our experience with installation of the kit was that it was much easier than we had figured it would be. The SYE kit can be installed with the T-case in the Jeep however since we were making the swap in conjunction with a new lift it was easier to remove the case and put it on the bench. The supplied instructions are clear and to the point. I would caution that you remove the front yoke nut while the case is still in the Jeep so that you have leverage working for you unless of course you have a good air impact wrench. I must also state that good snap ring pliers (both pin and flat types)are required and a great investment. Good pliers can be bought at most auto parts stores that are capable of both internal and external rings and come with multiple sets of replaceable tips for different applications. Consider it an opportunity to add a good tool to your box. We found all mating surfaces to be machined with the highest of quality and precision so as to provide a good sealing surface. Parts fit together with ease and once you have the case on your bench you can have the installation completed in less than an hour providing you have the above mentioned set of quality snap ring pliers. It is important to note that one really needs to follow the instructions carefully, especially the torque settings for the yokes. If not properly torqued the rear yoke will not hold the tone ring securely enough and erratic speedometer operation will result. With a good torque wrench and perhaps a pipe for some leverage, torque the rear yoke to between 180 and 200 ft/lbs, after the T-case is back in the Jeep of course. After a year of hard use on the trail we have had no issues with the Super Short SYE and our T-case shifts like it was new, perhaps that is coincidence but we will take it either way.
	Hint: If you have an air compressor and are using 1/4" disconnects, replace them with 3/8 fittings. The difference in the amount of CFM available to your air tools is huge. We were amazed that when we switched our shop over to all 3/8" fittings our cheap air impact driver was able to turn off and on the yoke nuts on our T-cases with ease. With 1/4" fittings the nut wouldn't budge.

If an SYE is in your future list of planed upgrades, then look no further than JB Conversions. For more information and comparisons go to JB Conversions web site or contact them at: JB Conversions, Inc. P.O. Box 2683 Sulphur, LA 70664-2683 Phone: 337-625-2379 Sales and Product information: sales@jbconversions.com