The GM TH400 automatic transmission adapter to the Jeep NP231 is 4.250” in length. The adapter material is 356 T6 heat treated aluminum alloy and has a provision for a transmission mount. The adapter kit includes an adapter housing, new 27 spline TH400 output shaft, 27x23 spud shaft, bearing, snap rings, gaskets, fastening hardware, and adapter instructions.
Note: this adapter kit is designed to replace the AX15 transmission.
Note: If the NP231 23 spline input measures 2.12” in length from the face of the transfer case, the input shaft must be modified “shortened” to a 1.50” stickout.
The adapter assembly will fit the Jeep NP231 transfer case with a 23 spline input shaft. This input shaft protrudes from the face of the transfer case 1.19”. Introduced in 1988, the Jeep NP231 is a part-time transfer case became the standard for XJ and YJ models. It was also used in six cylinder ZJ models through 1995. Chain driven with a 2.72:1 low range, it’s reliable even with more than stock horsepower applied.
This adapter kit is designed for exclusive use with the GM TH400 automatic transmission. The TH400 has a case length of 24.250” and a “Texas-shaped” oil pan underneath it. The factory output shaft has a spline count of 32 spline and had various output stick-out lengths.