OT Grand Cherokee V8 Question.

I have a 97 grand cherokee v8 that I drive in the winter. It has 211,000 miles and has been pretty much trouble free until now. At speeds over 55-60mph there is a horrible whining sound from the area of the transmission. I know the tranny in this car is not the strongest, but I have been very carefuly about having it flushed quite often. My father was the original owner of the car, and always maintained the tranny (and the rest of the car) properly. Has anyone got any idea as to what this problem could be? Will it make it through another season?

Thanks!

Mike