Transmission problem
1997 Ford F350 V8 Four Wheel Drive Automatic 253000 miles

1997 F-350 with the powerstroke, in the last several days the overdrive off light comes on by its self, sometimes it will not shut off, sometimes I have to shut off engine to get it to go off, I have had the switch replaced and there are no codes in the computer (it has been at a reputable transmision shop for 2 days now) the light never "flashes" which I know is a computer code/issue I am not sure if this is related but the tach "drops out" all the time, but it has been doing that for several months now and the overdrive light is new in the last week.