A transmission fluid change, sometimes called a transmission flush, should be part of your regular vehicle maintenance, just like an oil change or replacing the coolant in your radiator. Regular service can help you avoid costly transmission repair. Generally, you should have a service every 24,000 miles, or every two years. Some manufactures recommend longer service intervals like 50,000 or 100,000 miles. However, these intervals may exceed any opportunity for you to identify problems early ...