I have a 1993 4X4 Tracker that is in great condition but has developed a problem with the automatic transmission staying in first gear until the fluid or something begins to warm up. It immediately goes into first directly after cranking but as season changes and the outside temperature cools down is taking longer to change to second gear. It will even slip as in neutral until something warms up. Once it changes from first to second it shifts up and down without hesitation. What do you think mechanically is my problem and what I should do to solve that problem.