Got a 4R70w auto tranny and tried a WOT run on the highway today and it refuses to downshift or upshift at WOT. Drives/shifts okay at partial throttle. Did notice cruising at about 25mph that it had an ever so slight problem chilling at about 1500 rpm like it wanted to shift but would change its mind over and over again. Any thoughts. Time for a rebuild? Haven't changed anything with the transmission lately. I don't think it's tune related.
