I know this will start a big debate but I want to know everyone's opinions. I bought a used 2005 impala 3.4 auto transmission. 116k miles. i noticed the transmission fluid was dark and had what looked like dust particles in it. I used a transfer pump to pump out a gallon of the old and put in new dex3 fluid. A week later I did it again. the fluid appeared much better- still not perfect. I checked it again about a month or so later and it looked very similar to the first time i checked it- dark. i bought a filter and gasket set and dropped the pan. the magnet had about a 1/4" coating of particles stuck to it and the bottom of the pan was dirty as well. I cleaned it all, replaced the filter and this time refilled w/ Valvoline maxlife dex6. It held about 6ish quarts this time so more fluid got replaced. The only bad tranny symptom I encountered so far was a jerky takeoff occasionally which has not happened in a while and from looking at forums can happen. What kind of advice does anyone have about future maintenance? I am about 80% or so new fluid at this point with the majority of it being the allegedly better quality fully synthetic. my test drive afterwards seemed to have smoother shifts. Thoughts? Advice? Ridicule? Thanks!