97 Grand Cherokee Laredo: Transmission Hard Shifting In Wet Weather
 

I have a 1997 Jeep Grand Cherokee. The transmission works smoothly without any problem on dry days. Its fine on rainy days to until I drive through a puddle and the underside is sprayed with water. At that point it will hard shift and seem to be working in the wrong gears (while making aweful noises). Usually it goes away in a few minutes. Last weekend when driving in slush, this started again and the transmission did not start to work properly even after I got home. So I towed it to a local mechanic. He looked at it and really didn't seem to want to get into it. He said that the tramsission was failing and he thought it was internal. He did not do a diagnostic. The fluid level is fine and the fluid is a new pink red colour. The whole transmission is encased in steel. After hearing that the transmission was written off, I went to pick up the Jeep at the mechanics shop and when I drove away, the transmission worked smoothly and shifted perfectly on time.. What going on? It is directly related to something getting wet as the issue occurs immediately upon being slashed with water. Its been doing this for a year. Any help greatly appreciated.