2011 Ford Expedition RWD Transmission output shaft problem

[Deleted User]

My car is a 2011 Ford Expedition RWD, with a 5.4L engine and the 6R80 transmission. I started to change the oil in the transmission (the oil was brownish and it was the first time I changed it) when I noticed there is some slight up and down movement of the output shaft assembly. I unscrewed the output flange and observed that the shaft itself was moving up and down, as if from within the transmission. Is it normal to have up and down movement on the output shaft? I would think that, in time, if the problem isn't fixed, the seal there could break and leak oil. Is this true? I looked at a diagram of the transmission and noticed that there is a wide needle bearing in that location. Could this bearing wear down, and can it be replaced (if necessary) without removing the transmission from the car?