GM SM420 4 Speed Manual Transmission to the 1974-80 Land Cruiser 16 Spline Transfer Case Adapter Kit

Our GM SM420 adapter to the Land Cruiser 16 spline transfer case is 4.50” in length. The adapter material is 356 T-6 heat treated aluminum alloy, and the adapter has a provision for a transmission. The adapter kit includes an adapter housing, 16 spline spud shaft, bearing retainer, bearing, snap ring, set collar, gaskets, fastening hardware, and adapter instructions.

This adapter assembly fits 1974 to July 1980 16 spline transfer cases. The drive gear has 16 internal splines and a diameter of 1.259”. The transfer case bolt pattern is the same as the earlier 3 speed transfer cases. 

 

This transmission works great in Land Cruisers. The overall length is 10-1/2”. It has the lowest 1st gear available of 7.05:1; 2nd 3.57:1; 3rd 1.7:1, and a 4th gear ratio of 1:1. The transmission was used in GM trucks from 1947 to 1968. This transmission has a 10 spline output shaft which we couple to using a new spud shaft. (Note: We have seen a few SM420 transmissions with a 32 spline output which we can also adapt to). The cast iron case of this transmission will sometimes require modifications due to interference with the front driveshaft or transfer case shifter linkage. A transfer case shifter linkage bracket is not included in any of these kits. As the years progress, it is getting harder to find this transmission and parts.