So just recently, my automatic 93 4 cyl 22re 4wd 166,000mi started to stick in 3rd. I would be on the highway pushing the thing at 45-50 mph but it just wouldn't shift into 4th for probably 10 minutes - i guess it wants to warm up first or something. I changed the trans fluid, that didn't help. I hope this isn't just the beginning of the end, any suggestions?

 

Yep, there's a temperature actuator that holds it out of O/D until things warm up.