My owners manual states that I should change my transmission fluid and filter at 100,000 miles for a vehicle that experiences "normal" driving. My question is this- should I follow the owners manual on this or change out the fluid and filter at 75,000 miles? I just turned 70,000 miles and the fluid is not showing any signs of burnt material it it and it still looks and "smells" healthy. Oh, I would consider myself a "normal" driver as well. The vehicle is a 2004 Chevy Silverado 4x4 with the 5.3 L engine. Any thoughts?