the rule to bear in mind is the hotter it runs the shorter the life. one of the best rule of thumbs was given as outside temp + 100 degrees. normal operating temp should be around 170 to 200. never above 250 for extended periods of time. I have 2 tranny coolers and tcc lock. My temps run 155 in winter and 190-200 with 8k lbs in summer, in traffic it can hit 230.