Automatic overdrive in 1996 e-150
I just bought a 1996 econoline. The transmission does fine until it shifts into over-drive, then it vibrates the whole van. I can not tell if the trans is slipping or not. When I accelerate past 65 it is smooth as silk. It is also smooth with the overdrive off. Is the overdrive on this van a lockup tourque converter? Can it be disconnected?