I am experiencing an issue with the Overdrive in my 95 v6 4runner. It has started not shifting into Overdrive until the engine is completely warmed up. I don't think it ever did this before. Once warm, it shifts fine. But if it sits for a couple of hours and cools off, it will not shift into Overdrive until the engine temp is mid range. This may be coincedental, I am not sure.

Kurt

Test your ECT sensor. If that's good, try replacing your thermostat. It may be sticking open and cause slower engine heating.