I just posted a thread about the drain plug on the auto transmission, the damaged one being the result of hunting down an overdrive issue I have been having with the car.

When I purchased it, the kickdown cable was completely shot, so I simply disconnected it and stayed off the highways. I have since replaced the kickdown cable and totally guessed on the proper adjustment (but it seems fine). Up until this point there was no overdrive, no click of the relay behind the dash, and no light on the instrument panel indicating that I was indeed in overdrive.

Today on my way home from an appointment I had a chance to get on the highway for the first time since purchasing the car. Sure enough, it shifted smoothly all the way into 4th gear around 55-60mph. However, there is still no light on the dash, when I press the button nothing happens. As far as I know there is not a bypass kit installed on this car, but then again I don't know what I'm looking for. There is the one wire coming from the shifter down to the solenoid and that's it. The solenoid is covered in dirt and grease and everything else you would expect with 259k miles.

What are the chances that the light is burnt out, and the relay is indeed working properly as well as the solenoid? Because the overdrive did NOT work prior to the kickdown cable replacement, even if I manually pulled the cable all the way out.

I'm happy that the OD is working, but I have no idea how...

 

this OD circuit is frequently misunderstood.

the light does NOT indicate you are in overdrive. the light ON indicates that overdrive is DISABLED. and to further confuse things, the OD solenoid is powered exactly the opposite of the light. if the light is ON, then the solenoid is OFF, and overdrive is disabled. if the light is OFF, then the solenoid is ON, which enables automatic overdrive.

the OD relay is ONLY controlled by the button. if automatic OD is enabled, its always enabled no matter what speed you're going, but the actual shifting into OD (4th gear) is done hydraulically inside the transmission, and it will shift into OD/4th if A) the speed/rpm is appropriate and B) the kickdown cable isn't indicating you're asking for hard acceleration.

re: your kickdown cable... when mine refcently broke, it was stuck wide open so that the transmission thought I was heavy on the gas pedal at all times... because of this, the engine would stay in 1st way too long, then in 2nd way too long, even with no throttle.

the correct adjustment of that cable is such that there's a bit of slack in the kickdown cable when the throttle is at idle, and that if you push the gas pedal all the way to the floor, shortly before you get to the floor, you feel a 'notch' or resistance that you can then push through, thats the hard kickdown limit, and if you floor the gas that hard, you will force the car into a lower gear unless the RPMs are already too high.

 

Essentially what you are saying is that my OD circuit is not functioning the way it should, but that my overdrive is always on, which is not necessarily a bad thing. I feel the resistance when the pedal is near the floor, and it will down shift to a lower gear under hard acceleration. Everything seems to be fine, I just can't turn the automatic overdrive off.

 

the hack to fix a broken OD solenoid (or broken control circuit) is to dremel a slot on the bottom of the OD solenoid such that it acts like its always powered. the only way you could know this had been tone would be to remove the solenoid (and clean the heck out of the area around it before you do this as you absolutely don't want a speck of dirt getting into your tranny!!

here is a modified solenoid. the inner O ring has been removed, and a notch cut between the two holes...



another alternative is to remove the solenoid entirely and replace it with this plate from IPDusa...