introduced in 1936. One difference in the HD design is the dogs are slotted and retained their star outer shape. 4th is also stright cut. In a bike with all the wind and engine noise and no cabin to resonante in, straight cut gears are not bothersome. Most performance bikes still use this design as helically cut gears, while quieter, produce power-robbing side forces.
I wonder if the benefits of this design when used in a car outweigh the hard shifting and cabin whine.