This awesome piece of gearing has appeared on HowStuffWorks prior to. You could understand it from the electrical screwdriver short article. An automatic transmission is made up of two full planetary gearsets folded with each other into 1 component. See How Equipment Ratios Operate for an introduction to planetary gearsets. https://gearbox-auto18405.suomiblog.com/top-gearbox-auto-secrets-49770677