1998 Windstar speed sensor/transmission lot of detail

I have a 1998 Ford Windstar with a 3.8L & 95,000 miles. Just about a week or so ago, the speedometer started acting up shooting up and down until it would eventually go to zero and not come back on. After a few trips the speedometer would work when the car was cool but when it warmed up the speedometer would just drop to zero and stay there. When this would happen the transmission would not respond properly. The transmission revs high and shifts funny. We had a scanner put on it and the result was vehicle speed sensor a. We replaced the speed sensor and have had the same result. We have checked all of the wiring and do not see anything loose, cracked, chaffed, etc. Tonight we dropped the tranny pan and everything seems to be in normal order there. The fluid looks and smells fine and there is not an abnormal amount of metal on the magnet. I have found from looking online that there is a 2nd speed sensor. The transmission is AXOD. Where we thought the second speed sensor should go there is a cap. The sensor we installed is on the transaxle. The cap that we found is where you would find a speed sensor on an older model car (passenger side output shaft). Where exactly should we find the 2nd speed sensor? And do you know which sensor is "vehicle speed sensor A"? Any other advice would be greatly appreciated!