Hey Guys Im trying to see if there is a kit to make a orginal 4-speed to a open drive line? I haven't been able to find much on them.
The SM-420 was used on later GM trucks with open drivelines. You could get the output pieces from one of the '55 and later trucks (or the whole tranny) and attach it to your truck. I'm guessing you are doing this to attach a later model rear end with more highway friendly gears.
All SM 420 4 speeds from 1948 & up used an open drive line on the 1 ton & larger trucks. Locate a transmission from a big truck & the U joint will be ready to bolt up to a standard drive shaft.
The 3/4T used the torque tube on the front half and an open shaft on the rear. This lets you keep your torque tube trans but you will need a hanger bearing where the drive shaft changes from closed to open.
