96IL6

I have a 96 150 with 118600 miles on it.I replaced the filter and replaced the lost fluid that was lost during the process. My question has to do with a whine as it accelerates through the gears. It also does it during downshift as well. I was told there was too much play in the input shaft that is causing the whine. Am I on my way to a transmission failure, or am I missing something else? No codes or overdrive light flashing. Thanks for the info and input