With all of the new components on hand, we went to Rock-Tech Offroad where owner Chris Johnson carried out the installation of the rebuild parts, as well as the new Super Short SYE and the other internal beef-up parts. The end result was a beautifully prepared transfer case ready for even high-horsepower applications. You'll see more of the "NP231 Forever" transfer case in coming issues as we provide coverage of the aforementioned Jeep Liberty NP231/Klune-V conversion.
This stock NP231 out of a TJ had seen better days but was complete and fairly undamaged, making it a good rebuild candidate. The transfer case is equipped with a 23-spline short input shaft, which is what we'll need to properly mate it to the Klune-V in the Liberty. | 
The magnet in the case interior had collected a good bit of debris - another indication that a rebuild would be beneficial. Also note the slack in the chain in the background. | 
Chris Johnson of Rock-Tech Offroad removed the stock chain, drive sprockets, and output shafts as an assembly. |
Here, the stock three-pinion planetary (left) is shown next to JB Conversions' six-pinion planetary assembly. The six-pinion unit will do a better job of distributing the load since it can spread it across six gears instead of three. | 
The old chain and output shaft (right) is shown alongside the new, wider chain and output shaft. The increased width of the new chain is apparent. A wider drive sprocket (not shown) is also included in the wide chain kit. | 
The JB Conversions NP231J heavy-duty Super Short SYE is an awesome means of creating more rear driveline length. The kit includes a new tailhousing, a new machined 1310 CV yoke, and a new 32-spline hardened mainshaft. A new Honeywell electronic speedometer sensor is also included in the kit, as is a new custom tone wheel (not shown). |
The stock rear output shaft (right) shown next to the new JB Conversions Super Short rear output shaft clearly demonstrates the benefits of this kit. The new shaft allows for a much longer rear driveline, which reduces extreme driveline angles. The heat-treated shaft is machined to exacting tolerances and features a wider shoulder to support the speedometer tone wheel. | 
The heavy-duty Super Short SYE tailhousing is manufactured from 356-T6 heat-treated material and features a support boss around its perimeter that keeps the oil pump in a perpendicular position to the mainshaft. The stock housing is on left, and the new Super Short tailhousing is on right. The housing is partly responsible for the kit's full 3-1/8-inch-shorter length than other HD SYE kits on the market. | 
The donor NP231 'case halves were bead-blasted to remove the built-up grease and corrosion. A new input bearing from the master rebuild kit is shown installed with the stock input shaft and the input bearing retainer in place. |