My original SM 420 has 13 teeth on steel driven gear.This matches up to 5.14 or 5.17 rear ratio. According to my 1929 to 1955 Chevrolet parts manual they were available as sets of gears, from 11 tooth driven to 14 tooth driven; paired to a 4 tooth worm gear at the drive shaft yoke. They are not at all like the later Hydramatic 350 etc.Like I say got it close with a modified ratio adapter I built up myself, Im about 3 mph fast at 60 miles per hour and about 2.5 miles over on odometer in 100 miles travel. Can adjust speedometer internally to get the speed right and deduct 2.5 miles in a hundred to get fuel consumption correct enough!
Too poor to store buy a fix!
