TH-700 transmissions will downshift from fourth to third gear anytime there is more than half throttle (except Corvette and some Camaros and Firebirds). So it’s impossible to cruise at high speeds in overdrive (fourth). This prevents a forced part throttle kickdown from fourth to third gear, and allows cruising at higher speeds in over-drive. The transmission will only kick down from Fourth to third at 3/4 throttle.