TH400/JEEP NP 23T(WIDE)(AX15)

Advance Adapter

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, 27×23 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.

Transfer Case

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.

Transmission

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.

Bill Of Materials

• GM T400/4L80E 862-4709 GASKET / 716510
• TRUE ARC SNAP RING HO-315STPA / 716456
• GASKET-N.P.208 TRANSFER CASE / 716517
• LOCK WASHER 3/8 ZINC / 723704
• NUT 3/8 -16 PLATED GRD 5 / 723701
• SHAFT- TH400 OUTPUT / 52-3200
• ADAPTER- TH400 TO D300 / 51-6400
• SHAFT- GM 27SP TO JP 23SP LONG / 52-6301
• SNAP RING (T350 / T400) / 716450
• SEALED BEARING 209RS / 716308
• H.H.C.S. 3/8 -16 X 1-1/4 (GR5) zinc / 723722
• STUD BOLT 3/8 -16 X 2 LG B7 / 723711