My 1991 ford explorer won't shift when cold. The transmission was rebuilt three years ago. Payed $1800 for the rebuild. Now I changed the transmission fluid and filter. It seemed to get a little bit better then the next morning when it was cold, it would not shift again. I then had the transmission power surged at a trans shop and it seemed okay that day but again I'm back where i started. Now it won't shift again when it's cold. If I manually shift it in the morning it will shift from first, second, to drive. Someone suggested to eliminate the radiator as for cooling and to put an larger external cooler on. Haven't tried that yet but it doesn't seem like its going to help anyway. It doesn't smell burnt and it only has 120,000 on the truck. Does anybody have any idea what's wrong with this P.O.S.?

My explorer can sit and warm up for like 20 minutes and then i try to drive it and it takes forever to kick into gear. it will only go maybe 20 miles per hour. i have to let off the gas for this to stop and sometimes that doesn't even work. Its getting worse by the day. it sounds like its trying to go but it cant and there is a little whining sound when its doing this. then after it finally kicks into gear its fine until i come to a stop sign or a stop light. well, anywhere that i have to hit the breaks. then when i hit the gas it does the same thing as when i start it but its not nearly as bad. this just started when the weather turned cold. WHAT THE HELL IS THE PROBLEM???????? My husband and father in law just changed the transmission fluid and filter and the oil and it was fine the day they did it but the next day it was doing it again and worse. its driving me crazy because i don't have the money for a new transmission or another vehicle. What do i do to get this to stop????