88 tranny problem

Hello, hopefully someone can help in this situation, I have a 88 with an auto and the sport/economy/123 switch. on start up when cold i must use the 123 mode as the other 2 will not shift out of low! when running in this mode if i switch into either economy or sport when at speed nothing! it just slips. after about 15 min it will go into either mode and work fine till i let it sit for a couple of hours!Is it a switch problem ( i DON'T THINK SO) or is it as simple as a new filter( hope so) but I need to know if I need to procure another one as this is a fine car and worth keeping.