Chevy Tracker Transmission Problems

[sellanycar]

My 90 Tracker has an auto tranny. I goes into low gears fine and pulls well, but when driving it on the highway it trys to shift into 3rd gear and there is nothing. Almost like shifting to neutral. Any suggestions appreciated. The previous owner drove it through high water and I believe that some of the water go in the tranny. Could that have burned up the fiber clutches?