Originally Posted by 1bmw1
Auto trannies should not have their oil changed unless it's opened up for another reason.
That is completely wrong. Auto tranny fluid should be changed in regular intervals no different than, oil, brake fluid, ps fluid, diff oil, etc. It goes through heat cycles just like any of the other fluids and does degrade causing air bubbles to be trapped in it which increases the temp of the fluid, and causes seals to swell. Once the old fluid is replaced, the seals are no longer as swollen and leaks develop. Changing the fluid before it gets to that stage prevents these leaks and other problems. Lifetime fluid only exists if you are satisfied with a 160k km life expectancy for your tranny.