Mitsubishi Repair: 1991 Eagle Talon Overdive Issue, overdrive switch, older cars

Question
I have a 1991 Eagle Talon non-turbo fwd and I have been having transmission problems lately. When I was driving the car it would drive in first gear and then it would not shift into second and would just continuously rev up as if I was in neutral. Now I have found out that I had been driving with overdrive on, so I turned it off and it seems to drive completely normal with it off, for now at least. Still now anytime I switch on Overdrive the car will go nowhere, will not shift, and will continuously rev until I turn overdrive off.

Any idea on what might be causing this problem, and how it can be fixed?

Thank you in advance.

Answer
Owen,
This sounds like perhaps the solenoid that the overdrive switch controls is not functioning properly.  I would recommend you have a transmission shop inspect your tranny.  It may be as simple as a fluid flush and filter replacement.  Though it could be as serious as needing a tranny rebuild.  On a car that's 17 years old, many mechanics would recommend replacing the existing replacing tranny with a used or rebuilt one.  Mitsubishi is discontinuing the manufacturing of many of its parts for older cars, so if your car needs major tranny work, buying a used one may be your best option.
Good luck!