1997 to current GM 4L60E/4L65E 4wd to NP231 transfer case; California Residents: WARNING The 4L60E hex bolt adapter to the Jeep New Process transfer case is 4.00 in length. And the overall length of the transmission and adapter is 25.875 inch. Adapter material is 356 T-6 heat treated aluminum alloy. The adapter has a provision our H.D. transmission mount. The adapter kit includes a 2 piece adapter housing, Jeep NP231 input gear that is 27 splines , GM VSS sensor, reluctor ring, O-ring, gasket, fastening hardware, and adapter instructions. Transfer Case: Jeep NP231 (21 spline) [AX5], Jeep NP231 (23 spline) [AX15] and Jeep NP231 (23 spline) [NV3550 and TF999]. Transmission: GM 4L60E Late Model (1997-2007).