It is very important to flush your transmission. The fluid of your transmission should be changed after every 30,000 to 60,000 miles like you change other fluids in your car. The transmission fluid work like a lubrication oil in the transmission. It allows all components to run smoothly.
We can say that the transmission fluid is a blood of the transmission. It protects and cleans the surface of the metal to wear. Lacking transmission fluid may harm your transmission from various types and can increase lots of problems. Like leakage of transmission fluid, unusual sounds, problems in shifting gears, overheating of transmission and etc.