50-6401 : GM TH400 to New Process 231 21 spline transfer case Adapter kit (1.25 long) (#50-6401)

50-6401 : GM TH400 to New Process 231 21 spline transfer case Adapter kit (1.25 long)

Advance Adapter
Our Advance Adapter 50-6401 will allow you to adapt a GM TH400 3 speed automatic transmission to the Jeep NP231 transfer case. The adapter housing is 1.250” in length and is manufactured from 356-T6 heat treated aluminum alloy. We also supply a mounting provision on the bottom of the housing to bolt-on our heavy duty transmission mount (716008). The adapter kit includes an adapter housing, new 21 spline TH400 output shaft, gaskets, seal, fastening hardware, and adapter instructions.
Note: If the NP231 21 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.
Transfer Case
The adapter assembly will fit the Jeep NP231 transfer case with a 21 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.
The Advance Adapter kit is designed to fit Jeep New Process 207.
This adapter kit is designed for exclusive use with the GM TH400 automatic.

1)1987-06 General Engine Conversion Information

4) New Process 231

2. GM TH400

Top Review


by Bill B, from Milwaukee Wi

Good adaptor

Back in 1991 my 1988 Jeep Wrangler had a 4.2 AMC engine and a Peugeot 5 speed, which twisted the main shaft spline, . I bought a junk yard Jeep Quadratic GM Turbo 400 for $100 and had it rebuilt with this kit to match the NP 231. It work so good I didn't need to change the drive shaft length. original length 23.5 new 24.5 length, and still works today

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