u/KatsupPacket

I know this is probably a stupid question but why cant you basically just remove the drive shaft off an axle and either bolt on an electric motor solid to the axle where the drive shaft input would normally be, or have a frame mounted motor with its own shaft that goes to the original existing mounting point for the drive shaft? Would you maybe need a step down gearing? I can clarify in the comments if I did not explain what I am asking properly.