also keep in mind though it may not be dirty, burnt or broken down now, but in another 10-30k it will be broke down, burnt and dirty then. if you are looking for life from your tranny you really should flush and do 100% fluid exchange. just to drain and fill is basically defeating your purpose. that is like mixing hot beer with cold.
if you just drain and fill you should just dump some trans fluid with 15k on it in. that is what you get when you mix new and old.
your fluid is still going to be dirty, just not as much.
also keep in mind that trans fluid also helps to decipate heat. A hot transmission does not operate as effecient as a cooler one. clean fluid will decipate better that half dirty and half clean.
just keep all this in mind when changing your fluid.
