I have 98 windstar with 200K miles and original transmission... which could be a record?? The transmission had some bucking issue from 1st to 2nd as far as I can remember but we drove anyway. Almost a year ago, on a very hot day, I was driving ~80mph on an interstate highway and OD light came on. We were about ~200 miles from home but fortunately we made it. What we did was that we let it cool down, and the OD light did not come back on. After that incident, the pan was dropped and transmission oil was partially replaced. We have not driven the van too far in case it breaks down completely. As I said, that was a year ago.
The OD light came back on a couple of times since. Now the weather is getting warm, the OD light comes on more often. But we drive anyway. If OD light comes on, we turn off the engine and let it cool down for a few minutes. There is no burnt smell and no metal shaving on the magnet at all. But it is clear that something is wrong because you can feel the transmission is slipping in OD mode before the light comes on. I am considering a complete fluid change. But not sure if it is worth the $$. I hope it last another year.
Other that the problem, the van has served us well.