An automatic transmission still has to shift, but the transmission does the work for you, so you don’t have to. Like the job of a manual transmission, an automatic transmission controls gear function, your vehicle’s speed, and your engine’s torque. It controls the different gear ratios as you accelerate and decelerate. The difference between an automatic and manual transmission is their gears. A manual transmission has different sets of gears that unlock and lock to achieve different gear ratios. An automatic transmission has the same set of gears that can produce various gear ratios. A planetary gearset is what causes all the different gear ratios in your transmission. The planetary gearset is named after its design, it has a sun gear, planet gears, and the ring gear. The center gear is the sun gear and the planet gears are around the sun gear, then the ring gear encircles all of them. The automatic transmission has what is called a compound planetary gearset, which still has one ring gear, but has double-sided sun gears and double-sided planet gears. The double-sided sun and planet gears allow for a larger number of possibilities for your gear ratios, which is why an automatic transmission is different from a manual transmission. The planetary gears in automatic transmissions work with bands and clutches to hold the gears in place to achieve various gear ratios according to information received from the valve body. The valve body receives from your vehicle’s brake function and speed for the planetary gearset to know what gear to use for that function. If your automatic transmission is having trouble shifting, making a grinding noise, or seems to be acting weird, you should give the experts at Eagle Transmission Repair Shop call today. It is never good to ignore a vehicle problem, especially a transmission problem. Call us today for a free initial transmission check! Serving Dallas and Surrounding Aears including Ennis Tx.