Transmission Fluid Dip Stick is a long metal rod that goes into the transmission. It serves check how much transmission fluid is in the transmission. The dip stick is held in a tube; the end of the tube extends into the transmission. It has measurement markings on it. If you pull it out, you can see whether you have enough transmission fluid, or whether you need more by the level of fluid on the markings. Most manual transmissions do not have dipsticks, instead they use a filler hole which is at the same level as the correct oil level. When the oil is topped up or refilled, the mechanic simply adds oil until the filler hole's level is reached.
Automatic transmission fluid is a specially formulated oil containing numerous additives to withstand grueling operating conditions. There are several different types of automatic transmission fluids and should be used according to the recommendation in your car's owner's manual. Automatic transmission fluid serves a multitude of purposes. Among other things, it cleans, cools, lubricates, transmits force, transmits pressure, inhibits varnish build-up and protects the transmission on a day-to-day basis