Just thought I'd pass along a thought. My indie shop switched from full flushing of all of the fluid every 30k, to partial fluid changes every 10k. Following that idea, I have started to change part ot the T-fluid at every other oil change, using the simple expedient of my Topsider oil vacuum pump - just push the pick-up tube down the trans. fill tube and suck out about 3 1/2 quarts in couple of minutes with absolutely no mess. So far I've got up to 40k using this method and the fluid is staying just like new on all of the cars. The Topsider is cheap and readily available at boat stores, Wall mart, etc ($35+/-), and makes oil changes quick and mess free as well. MB and BMW both recommend vacuum oil changes over draining through plug and the tests I have done show it does get everything out of the pan.