transmission acting funny
 

So my buddies is selling his 97 ram . Its one owner . Last year he had a trans flush done using bg universal fluid. He says ever since when He gets in the truck and starts it and goes quickly when freezing cold outside. When he goes to pull on the road it'll Rev a little before it grabs and goes. If he let's it warm up first even for a couple minutes it wont do it. Could it be fluid? Or something else? What do you guys think? Thanks all glae to be here