Transmission fluid should be replaced on schedule to avoid causing damage internally to the transmission due to dirty fluid. This schedule can be different for every car, as can be our recommendation regarding at what mileage this service should be performed. Additionally, there are many different designs to transmissions and how their fluid is serviced. The majority of transmissions are best serviced using our flush machine, which replaces the dirty fluid with clean, not only in the fluid pan but also throughout the transmission as well as the lines. Some transmissions cannot be serviced this way, however, and must have the pan dropped and the fluid and filter changed. Other transmissions require simply draining the fluid and replacing with new fluid. For specific questions regarding your transmission service, feel free to contact us.