The transmission on our modern vehicles still do the same jobs they have for a long time. Those jobs are. To regulate engine power transferred to the driving wheels to give the best possible power and fuel economy. To connect and disconnect the engine power to the driving wheels. And to change direction of power for reverse. Both automatic and manual transmissions must do these tasks as smoothly and quietly as possible. They must operate in extreme temperatures. They must also be expected to do this trouble free for a long time. An automatic transmission does this very little input from the driver while a manual transmission is completely controlled by the driver. A manual transmission uses on a fluid to lubricate and cool it’s internal parts. An automatic transmission uses fluid for the same purpose but it also uses the same fluid as a coupling to the engine and for hydraulic pressures to change the different gears. Most manual transmissions use a synthetic fluid that rarely wears out. However working parts do wear. As parts wear away they turn into very small particles. These particles mix with the fluid and after lots of wear can become a soup of worn particles. The more particles in the soup the faster parts wear. Automatic transmission fluid is not synthetic based and does wear out. It also can become a soup. Since automatic transmission fluid acts as a fluid coupling and for hydraulic pressure to work the gears, as it becomes worn it effects the way a transmission operates. This process is slow enough for a driver to not know it. If the fluid gets worn too badly or becomes soup it can damage the working parts of a transmission and be very expensive to repair. For these reasons we recommend transmissions be serviced regularly. Manual transmissions should be serviced about every 60,000 miles to 90,000 miles depending on the loads they pull and the conditions they operate in. More often under heavy loads or in dusty or off road conditions. If they are operated in moderate conditions the service intervals can go up. Automatic transmissions service intervals are more important. They should be serviced about every 30,000 miles to 60,000 miles depending on the loads they pull and the conditions they operate in. More often under heavy loads or in dusty or off road conditions or a lot of around town driving. If they are operated in moderate conditions the service intervals can go up. Our manual transmission service will exchange 100% of the fluid. Our automatic transmission service will exchange about 40 to 60% of the fluid in the transmission and replace or clean the filter. Our automatic transmission flush will exchange 100% of the fluid and flush a cleaner through the transmission, cleaning the internal working parts. We recommend the flush be done about every other time.