NP231J HD Super Short SYE

HD Super Short SYE

Part #16-1201-1945 -- $375.00 (w/1310 CV Yoke)

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Part #16-1201-1951 -- $395.00 (w/1350 Non CV Yoke)

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Part #16-1201-1967 -- $475.00 (w/1350 Rear Output Flange)

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Since 1994, our company has sold the "HD Slip Yoke Eliminator" kit for all models of the NP231 transfer case. With many thousands of HD kits on the trail, we have had 100% success with not one failure. The target market of our original HD SYE kit was the Jeep YJ and TJ. The typical Jeep suspension lift in past years was 3.5" to 4". Suspension companies have now moved into the next level of design often call "long-arm" kits. These new suspensions yield high travel and high lift. The HD SYE kit that was once more than adequate is now coming up a bit short. For suspensions in excess of 4 inches, we have designed a new HD SYE kit that shortens the overall length of the NP231 by another 3-1/8" over the standard HD SYE.

Yoke Comparison

JB High Clearance CV Yoke


  • The new 1310 CV end yoke supplied in the kit has been redesigned from the more common Spicer 2-4-5341 yoke (shown on the Advance Adapters, Inc. kit photo - left).
  • Our new yoke has additional clearance for those of us needing a high angle driveshaft. The new JB Conversions, Inc. yoke is also shorter than the competition.
Super Short SYE

Notice the length reduction of the new SHORTY kit over the conventional HD SYE kit.

Super Short SYE

With the SHORTY kit installed, driveline lengths can exceed 22”.

NOTE: The overall length of a NP231 equipped with our Shorty SYE kit is shorter than an Atlas II

Super Short SYE

Our new shorty SYE kit features the time proven, 32 spline output design. The mechanical speedometer has been replaced by a typical hall effect speed sensor and custom tone wheel. The electrical pulse generated by the speed sensor is recognized by the Jeep speedometer instrument as stock therefore operation is smooth and reliable.

Super Short SYE

The longer shaft is a stock TJ shaft. The middle shaft is the current standard HD SYE shaft.
The shortest shaft is found in the new SHORTY kit by JB Conversions, Inc..

An added benefit of the new electrical design is in the flexibility of speedometer calibration. Signal converters from Dakota Digital, Inc. and Superlift Suspensions can be easily connected into the Jeep wiring loom (only 3 wires) for easy adjustability.

** It is important to note that the signal converter is not necessary to have a functioning speedometer with our new kit. It is only necessary for adjustability necessitated by the changing of tires and/or ring and pinion gears.

Super Short SYE

The speed sensor supplied in the kit produces the stock Jeep signal allowing the original speedometer to function normally.

Jeep Wranglers from 1987 to 1991 utilize a cable driven speedometer. For these applications we recommend the VDO electronic speedometer as a replacement. The VDO unit has its own adjustment features eliminating the need for the signal converter mentioned above. The VDO unit is the same size as the stock speedometer and can be installed in the factory location behind the plastic dash panel. The illumination is a bit better than stock and the face matches stock very well. Installation is a snap with no wiring headaches.

If you are in the market for a complete transfer case, please review our other web page featuring the NP231HD sold fully equipped with heavy duty internals and the HD shorty SYE.

Why Superior Engineering Wins - Every Time

Recently the JB Conversions, Inc. Super Short SYE has been compared to a new entry in the ultra-short SYE market. Various web postings and new product listings make reference to our product suggesting similarities in design and function to this other short SYE kit.

The following review provides information and comparative photos featuring our proven product. The Brand-X kit incorporates several design approaches which we feel are very inadequate. Many of the attributes used by Brand-X to reduce overall length were considered and rejected by our company in the early stages of development of the JB kit. We want to make it very clear that these deficiencies draw absolutely no similarity to the superior design offered in the JB Conversions, Inc. Super Short SYE kit.


The internal spline area of the JB yoke maintains a thick cross-section. Also notice the internal spline length of our yoke vs. Brand-X.


The new bearing housing in our kit is cast aluminum heat treated to 356T6. As evident in the cross sectional view of the two castings, the JB bearing housing is much thicker and therefore stiffer than the other brand. The additional material adds cost as calculated by weight, however, we feel the strength gains are worth the investment. You've invested heavily in your rig. Why cut corners now?

In either housing, the rear support bearing is held in place by an internal snap ring. The casting material on each side of the snap ring groove holds the bearing in place under thrust load. It is best to beef up the casting on both sides of the groove for maximum strength. The JB kit offers substantial reinforcement in this area over the other brand.

The rear oil seal must be seated squarely in the casting bore to achieve a leak-free seal. Our housing provides an internal boss which allows the seal to be pressed into the bore until it reaches the machined surface of the boss. This ensures that the seal is properly aligned with the end yoke after installation. Should the customer need to change the seal over time, the internal boss will make this exercise easy to accomplish.

Pump Compare

The NP231 internal oil pump holds the key to a long lasting transfer case. It is imperative that this oil pump be supported in a perpendicular position to the mainshaft. Our bearing housing follows the design of New Venture Gear in providing a distinct support "shelf" or boss around the inside perimeter of the bearing housing. This raised boss is intended to support the pump and hold it in proper position with the mainshaft. The four tabs on the oil pump are responsible for keeping the pump from rotating in the housing. These tabs are very thin and are not intended to align or support the pump.

Bore Compare

The speed sensor in our bearing housing is a high quality speed sensor produced by HONEYWELL, Inc. specifically for Chrysler Corp. This speed sensor maintains a viton O-ring which seals the sensor in the bore machined into the bearing housing. In order to provide a smooth bore for the sensor O-ring, our bearing housing has a high tollerance micro-finish for the machining specification.


This is the HONEYWELL speed sensor compared to the cheaper sensor used by the other brand. We could have used a cheap sensor like the one on the left however we didn't want to run the risk of creating problems with "check engine" lights or speedometer issues. The HONEYWELL sensor cost is 4 times that of the "all plastic" piece on the left.

Notice the difference in the two speed sensors. A hidden benefit of our chosen sensor is that a replacement can be obtained from any Chrysler dealer anywhere at any time. Sensors do not hold up well to high heat therefore care must be given to the routing of aftermarket exhaust systems and catalytic converters.


The tone wheel used in the JB shorty kit is machined from pre-hardened 4140 alloy and provides 8 oversize oil passages. The tone wheel works with the speed sensor to produce a speed signal and it also acts as a spacer below the output bearing. When the yoke nut is tightened, the shaft is drawn outward forcing the tone wheel to become compressed between a shoulder on the mainshaft and the bearing itself. It is important that the tone wheel be made from a hardened material such that it is not deformed or dented when the nut torque is applied as is evident in the Brand-X tone wheel (see below).


As mentioned above, a shoulder is machined on the mainshaft to provide support for the tone wheel once the yoke nut is torqued to 200 lb.ft. The JB mainshaft maintains a substantial shoulder to support the hardened tone wheel. If this shoulder is too small or narrow, it may cut into the tone wheel (as shown above in the Brand-X tone wheel).



Direct Oil Compare

The custom tone wheel used in the JB kit is designed for maximum oil passage. We use 8 large bore holes machined into the tone wheel in an array which places the holes directly over the balls in the rear bearing.

Shaft Compare

In the mid 1990's, New Venture Gear changed the mainshaft bearing design on most all of the 231 and 241 series transfer cases. This OEM design change eliminated the drive sprocket needle bearings located between the drive sprocket and mainshaft mid section.

With the elimination of the needle bearings, the oil outlet port in the lower portion of the mainshaft was also eliminated. Eliminating the lower oil port increases oil pressure to the mainshaft oil port located directly underneath the drive sprocket where the needle bearings used to be located. With the elimination of needle bearings, it is very beneficial to have the added oil pressure between the shaft and sprocket. Following the factory design, the JB mainshaft also eliminates the lower oil port hole.


The output bearing in all SYE kits is kept in place by a retaining ring. The output bearing retaining ring used in the JB kit is a "captured" ring. This thick snap ring is contained within a groove within the bearing as opposed to being located above or below the bearing as seen on the other brand SYE. With the JB design, it is impossible for the retaining ring to come out of the groove in the event that the ring failed.



The last line of protection in a transfer case is the oil seals. The rear main seal in the JB SYE kit is a double lip seal. The positioning of the seal on the JB kit is well within the "grind" section of the yoke.

The single lip seal on the Brand-X SYE is a single lip design and is positioned on the bottom 1/8" of the yoke.

An added advantage of our double lip seal is preventing contaminents, such as water, dirt, and mud, from gaining entry to the bearing.

Additional Info

Installation Instructions

Install Instructions

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