Your owner's manual can give you specifics on when your car is likely to need transmission service. More broadly, your car might be due for transmission service if you experience any problems or strange noises related to your transmission. You might notice an unusual grinding sound when you shift gears, which can be the result of an issue with your transmission fluid. You might notice that your transmission is a bit sluggish. You might notice some slippage when you shift gears. Anything about the process of shifting gears that seems out of the ordinary could be the cause of a transmission problem, so we encourage you to schedule service with us right away if you encounter any issues.