Mitsubishi Repair: 1994 Mits Expo wont go into Overdrive, shift into overdrive, worst case scenario

Question
1.8L Expo automatic transmission that will only shift into Overdrive when the car is really warm. It never goes into Overdrive when the weather is cold.  When I press the overdrive button in, it goes into a neutral like position when it doesn't work.  When I depress the button on the shifter the car goes back to high.  The transmission does not slip and seems to be in good shape otherwise.

Answer
Karl,
The best case scenario is that your overdrive switch is malfunctioning, and simply needs to be replaced, along with flushing your transmission fluid and replacing the transmission fluid.

The worst case scenario is that you have a band or solenoid in your transmission that is broken and not engaging your overdrive.  Your transmission has 3 gears, and when the overdrive is engaged, it simply links 2 or more to the gears together to achieve overdrive.  It would seem that something is preventing that from happening when the engine is cold, and simply making the gears spin freely as in neutral.

I would recommend finding a transmission shop to inspect this problem.  It may be a simple $100 fix, or could end up costing you a couple thousand for a transmission rebuild.  But get the inspection from a transmission professional before performing any repairs.  And don't be afraid to get more that one opinion from more than one transmission shop.
Good luck!