I have a 2000 Ford Ranger, 3.0L, automatic transmission. Approx 132,000 Miles. Tranny fluid level is fine. With no warning I lost reverse and the truck will not shift while in overdrive. If you manually turn overdrive off...truck works great. It will go in reverse but the rpms can get pretty high in the process. Also if on the highway going at least 45-50 the truck will begin shifting again with the overdrive turned on. Is this something easy like a torque converter or am I looking at a new transmission?