When I worked for an independent transmission shop, all th guys there told me Aamco was an acronym. It stood for All Automatics Must Come Out. If this helps any. Is your temp guage working? Because it won't allow overdrive if it's not up to operating temperature, or at least off dead cold. Don't have my FSM handy, so I don't recall which of the plethora of senders/sensors gives the signal to allow OD. Make sure it's getting signal, and for some reason I was thinkin it was in the valve body??? Which requires a pan drop. <img src="/forums/images/graemlins/kewl.gif" alt="" />