The SM-420 is a heavy duty truck style transmission used in a variety of full size trucks. These were produced from 1947 to 1967. The SM-420 has a 1 1/8″ diameter 10 spline input shaft that comes out 6 1/2″ from the face of the transmission. The input pilot is 19/32″ in diameter
This rebuilt transmission comes complete with an Advance Adapter’s adapter to fit a D-18 or a D-20 t/f case, as well as a shift tower, and shift handle. If you are fitting this transmission to a small hole case you will need a special bearing adapter and a 307 bearing ($34) , if fitting to a large hole case you will need a T-86 retainer and a 307 bearing ($59). No core charge.
Replacement SM 420 w/o adapter $650.00
1st Gear 7.06 to 1 2nd Gear 3.60 to 1 3rd Gear 1.70 to 1 4th Gear 1.0 to 1