NP231 Slip Yoke Eliminator Kit, Rough Country 50-7907

This is the Rough Country 50-7907 slip yoke eliminator (SYE) kit for the NP231 transfer case used behind the manual and automatic transmissions in the 1987-2006 Jeep Wrangler YJ and TJ and the 1984-2001 Cherokee XJ. It replaces the factory slip-yoke rear output with a fixed 1 3/8in-32 spline mainshaft, a 356-T6 heat-treated aluminum tailhousing and a 1310-series CV yoke.

The problem it fixes is the stock NP231 rear output. The factory design uses a slip yoke that rides inside the tailhousing so the driveshaft can slide in and out, which works fine stock but runs out of travel once the Jeep is lifted and running bigger tires - the steeper pinion angle and longer slip travel puts enough stress on the yoke and rear output shaft that it can snap. Converting to a fixed yoke and a short CV driveshaft removes that failure point and cuts driveline vibration.

This kit requires an aftermarket CV driveshaft (Rough Country's extended-travel shaft or equivalent) - it does not work with the stock slip-style driveshaft. It is designed around the current NP231 output shaft design introduced in 1997; earlier NP231 cases can still use this kit if the needle bearings are removed from the stock drive sprocket first. Comes with the output shaft, tailhousing, CV yoke, bearings and hardware. You will also need 4 yoke bolts to mount the new driveshaft - they are not included and are the same size as the stock front driveshaft bolts.