The biggest enemy of any transmission aside from deliberate abuse is heat. Three years ago I had the 727 in my Coupe rebuilt and simaltaneously had the largest stack plate transmission cooler B&M makes installed. After three scorching Texas summers and several 100+ mph runs down I-10 & I-45 the fluid still has the colour of pink lemonade. The tranny still shifts the same, no slippy slide or mushy shifts firm as a cheerleaders butt. Marc '67 Coupe