A transmission service belongs to your regular maintenance, much like an engine oil change or changing the coolant in your radiator. Regular service can assist you prevent expensive repairs to your transmission. Typically, you should have your transmission serviced every 24,000 miles, or twice a year. Certain makes recommend longer service intervals like 50,000 or 100,000 miles, nevertheless, these intervals may exceed any chance for you to identify problems early on so you can avoid minor problems turning into a major repair. Consider a transmission service as you would an engine oil change; a part of a regular maintenance schedule.
Generally, a transmission service substitutes about 1/3 to 1/2 of the fluid inside the transmission and is adequate for a regularly-maintained transmission. You may also want to change the filter at this time as well. For more extreme instances you may take into consideration a transmission flush.