Visit the Lincoln Mark VIII Forum for more help
As most of you know, Ford did not design the overdrive wire on the Mark VIII’s very well. The wire would rub against the metal substructure near the shifter and saw the wire in half rendering the transmission Overdrive Switch inoperative.
This is on my 1994 Lincoln Mark VIII and should work on any year Mark VIII. This guide will help you fix this Overdrive Switch problem yourself.
Parts You’ll Need
Ford sells both the overdrive button and the overdrive wire separately. Part number for the button is F5LZ-7G550-AA and the part number for the new wire is F5LZ-7E276-AA. Both combined cost me around $50. It’s a bit pricey but the dealer is the only new source for these parts.
Remove the Shifter and Switch
The first step is to move the shifter back into 2 or 1 and set the parking brake.
Next, remove the trim from around the climate control unit. It just snaps out, so you can use your fingers or a small screwdriver.
Now remove the 2 screws that are holding the shifter panel trim to the console. Just move this trim to the side, you do not have to disconnect anything.
Underneath the 2 screws you just removed are 2 more screws that hold to console on at the front. Remove these. Then pull up the rubber mat in the storage bin. You will find 2 more screws that need to be removed.
Next, take a small flathead screwdriver and pry out the retaining clip on the back of the shifter handle. Pull up on the shifter and it will come off the shaft. Don’t worry if your shifter button comes out, the spring and button are retained when you reinstall the handle later on. Just depress the button fully while working the shifter back onto the stalk.
Now unbolt the shifter plate, there are 2 small screws at the back and one at the front. You need to do this so that you can properly route the wire under the console.
If yours is as bad as mine it should look something like this:
Slide the console back about 4 inches. You can now remove the other end of the broken overdrive wire. It has a retaining clip and a small notch that needs to be depressed to release it.
Now you can remove the old overdrive button and wire. Take a small flathead screwdriver and pry the button out. Make sure you are prying on the outside plastic and not the inside part of the button, especially if you are reusing the button. The button should pop out as a complete assembly. Now all you have to do is pull the wire down and the wire and plastic end assembly will slide right out.
This is what you will have left:
Installing the new Transmission Overdrive Switch
Take the new wire assembly and slide it up into the groove in the shifter handle. Make sure that the side with the electrode (white plastic piece) is facing the wall of the shifter. Next, push the overdrive button in fully.
When you are through, it should look like this:
Route the wire through the shifter panel hold where the shifter shaft fits through and pull it back and connect it. The rest of the install is the reverse of disassembly.
Congratulations, you should now have this light on your dash: