This awesome piece of gearing has appeared on HowStuffWorks before. You might understand it from the electric screwdriver posting. An automatic transmission is made up of two comprehensive planetary gearsets folded with each other into 1 part. See How Gear Ratios Do the job for an introduction to planetary gearsets. https://gearboxauto39517.blogerus.com/56298092/the-basic-principles-of-gearbox-auto