I changed my tranny fluid and filter at 25000 and again at 42000. The second time I installed a drain plug into the pan. Now I just dump the fluid every 10,000 miles and add the 4 or 5 quarts. I will change the filter every couple of years with normal driving.

 

I change my oil and filter every 30000. The filter is the main problem every time I complete a change. I may change it sooner if i notice odd shifting at times. The filter gets plugged and does not let the appropriate amount of fluid in. The vehicle always shifts better after a new oil and FILTER change. Its telling me something when it runs so smooth after a change. I'm at 180000 miles.