I have the same problem with my 1998 2.5 liter with the CD4E transmission. It is popping in and out of overdrive. It will be fine for weeks, then barely driveable. I flushed the transmission fluid - no luck. I even tried a very good additive ( against my better judgement! ) Lucas brand. No dice. I have access to Alldata and Identifix, and there were no TSB's or commonly related problems. I talked to a transmission rebuilder friend of mine. He says it is a high pressure transmission and the drums crack and it will lose enough pressure at times to cause this problem, and the transmission will need to be rebuilt. I have not done this yet. I just parked it out in the back forty until I decide what to do. I really believe it is a valve body or shift solenoid problem, but have been too lazy to dig into it. Good luck, hope I was some help.
