When we recommend that you receive a transmission service, we do it because of three reasons. The first reason is while doing a routine maintenance check over we usually notice that the transmission fluid is either really dirty or dark in color. Also the smell is a good indicator that the fluid has lost all its benefits and needs to be flushed or may require replacing the transmission oil pan gasket as well as filter. The second reason that we might recommend a transmission service is because of a certain mileage has been met, as well as required by the specific manufacturer of your vehicle. the last reason we would recommend a Transmission service would be from a customer complaint of slipping and we want to try and make sure there is not a deeper problem then just contaminated fluid. When preforming a flush it is more beneficial because it is a full fourteen quart system flush. It completely replaces all the fluid with new fluid and we also include an additive to provide better protection for your transmission, as well as smoother shifting.