Hey folks, I picked up my corvette about a year ago and when I purchased it the seller informed me that the overdrive switch had gone bad and been removed. He only had the car for a year and didn't get around to replacing it, so now I'm doing it. I just have a few questions to make sure I understand this all correctly because I know that how the overdrive functions varies by the year (mine is an 86).

I'm in the middle of replacing my clutch right now and I noticed on the transmission the connector for the overdrive solenoid had come out and melted a bit, so I'm not sure if it will still work properly. I'd like to keep the overdrive as an automatic system instead of manually controlling it if possible, unless there is some reason I would really want to do so I don't know about. Does the wire that connects this solenoid go to the ECM, and that's how it controls the overdrive? I've also noticed that there is what I believe to be some kind of vent tube coming off the top of the overdrive unit. I'm unclear as to whether or not the end of this tube is meant to connect to anything or if it just hangs freely under the hood.

My car has an aftermarket Lingenfelter intake manifold on it, and as I understand some work was done to the electronics to accomodate this, so im not sure if that would somehow impact the ECMs decision making when controlling the overdrive activation, if that makes sense.

It appears that a previous owner also attempted to put in his own overdrive switch by taking two black wires from under the center console and soldering in a button on one of them, though this doesn't seem to do anything at the moment, I assume because it was disconnected at the solenoid the whole time. I went ahead and bought a proper button replacement for the shifter but haven't gotten around to tearing out the console to install it yet, so I have no idea what is going on down there.

I guess my question is, am I missing anything? Would getting the overdrive working (assuming it has no mechanical issues) be as simple as plugging in that connector and installing the switch, or is there anything else I'm missing? I can try to provide pictures and any other info anyone might need. Just getting very confused by all the variances by model year and any other slight changes etc...

Thanks in advance.

 

Step 1 Un-Monkey the Previous Owner, if the plug is truly melted and you cant find a replacement you can cheat it Ugly with a Cheap wire connector or a older single wire oil pressure sender/Switch off of a junkyard GM
If have a real early 86s that still has the switch it's a easy install, if in the shifter it can be a bit of a challenge to get the switch to move freely but you will survive it. with the trans out its a good time to properly flush out the lines and service the Fluids in Both half's of the Trans. I'm sorry you didn't make this post before you had the trans almost out, because with the switch being installed you could have tested the the Plug was getting voltage to the OD Solenoid and the OD was functioning correctly.

As for the Breather Tube it just slides up the firewall

 

OK, I've got it plugged in and everything reassembled. The car is still on jacks because of another issue, but I can start it up now. When the car is running and I activate overdrive, is there a light on the cluster that is supposed to come on? Or would I only know by getting up to speed and seeing that my rpms change?

 

Unless you can shift it into 2nd 3rd or 4th gear on jack stands once the coolant temp is above 175⁰F you won't see the light come on. Probably have to wait for a road test for safety reasons

 

As mentioned the car needs to be warmed up above 30 (27 actually) and above 2nd gear. You should have an OD light show up during lamp test when key is cyled on and I believe a OD off when it's turned off.

you can test if the command to OD with a simple test light or volt meter

 

Alright, I did a test drive and it didn't come on. I've also never seen that light turn on when I turn the key, ever. I assumed it's because the system was disconnected. Would you be able to provide me a diagram of what it is exactly I need to be testing?

I'm also currently still using the switch that a previous owner wired in, not the replacement I purchased. I'm going to try and put that one in, hopefully tomorrow.

 

As a test, all you need to engage the OD is +12 on the white connector next to the fill plug. The OD has to have enough internal oil pressure or it won't engage. Have you made sure it's full?