I've been trying to get my overdrive working on my 84. The DSPO replaced the crossfire with a quadrajet (from an 86 Dodge, no less)
First step was to get wiring schematics, which a gracious forum member sent me.
I found the OD relay was disconnected and the entire wiring plug was gone (just had a slew of cut wires) so following the wiring diagram, I just soldered wires directly onto the relay.
Took it for a drive. No OD. I'm 95% sure I followed the correct wiring. The only issue is there are two tan/black wires in the bundle, but I tried them both.

so I pulled the console I looked at the switch. cleaned the contacts,put it back together... no dice.

For some odd reason, I went into the fuse panel. Lo and behold the fuse for the ECM was missing. replaced the fuse. still no OD (but I do have a check engine light and fasten seat belt light, even when they are).

I looked at the switch again. No matter the location of the switch, I do not get a short across them.

I also do not have +12Vdc on the pink/black at the relay. According to my schematics, the pink/black uses the +12 from the age fuse (which is good)

any ideas?

to be fair. It runs really well as it is, except for the 3500 rpm at 65.
and while I have your attention what should be normal operating coolant and oil temps be?

 

First of all, I commend you for buying someone elses' butchered car. it takes a real car nut to do that.
your ECM needs input from the vehicle speed sensor and other sensors. make sure they are plugged in and functioning.
you understand that you can put in a manual switch and a couple relays to turn it on and off just to briefly check to see if the 4+3 is working.
buy a fuse holder and put a 15 amp fuse in it and tie it to positive on the battery. Then run the wire to where you can safely reach a switch in your driver seat, and put that wire on one side of a switch.. Then run another wire from the switch out the door and under the car to the first gear switch on the trans side cover.
then out of the first gear switch to the single blade coming out of the trans on the left side just above the pan on the plastic connector.
when you get it up to speed about 35 in second, push in the clutch, flip the switch, and let the clutch out. If your RPM drops, your overdrive works.
Now you know you have to find the electrical problems associated with the injection removal. if it doesn't work, it's overhaul time or the pressure switch in the trans is no good......or it's low on fluid, the clutches are shot, the seals are hard or the pump isn't working. Usually, it's either good or not.
to make these transmissions last, always electrically switch the trans with the clutch in or the car not moving.
Is the original distributor still in it?
if not, the ECM doesn't know the engine is running because the cam position sensor is the distributor. No distributor input means the engine isn't running, so no fuel, no overdrive.
I think you need to hook the trans up with some relays and make it totally manual.
BTW, there is a pressure switch in the trans. The solenoid is in line with that pressure switch. the solenoid will not see any volts until the pressure switch is made, so that's why the trans does not "spark" when you put 12 volts to it.

 

I didn't know it was this bad. My wife bought it for me in Indiana, sight unseen to me. She felt bad that I was forced to sell my C5. She told me it was in great shape and ran good.
Oops.

The DSPO was a mechanic though.
I'll have to look at the distributor.
here's a pic, don't know if you can tell from it:

 

any instructions on this?

and how do I get to the ECU? I know it's behind the breadbox, but I can only get the bottom panel off and I find wires and plugs.

 

The distributor in the photo is NOT the right one. It looks like all the sensors, for the fuel injection unit, are gone. As said before, you can install a switch to operate the OD.

Good Luck

 

I could have told you that


pic of wiring harness on passenger side of engine:


driver's side:

 

Boy..Im remember the dreaded 4+3 Doug Nash of my days with a 86 1\2 C4.

I have the same issue one day when my OD stopped working.
The OD light would come on but wouldnt go into any OD gears.

The problem with mine was the OD unit and 4 speed has a seal that let go between the 2 and gear oil dump into the OD unit destroying it.

I would drop the pan on the OD unit and see if this happened to your tranny.

BTW.. Boy someone butchered the harness Why did the cut it like that instead of moving out of way.

 

I wish I knew.

from what I understand, at present my issue is electrical, since I cannot even get a light.
If the OD unit is terminally destroyed, then I lose reverse, which works just fine.
I am going to attempt to bypass the whole ecm/relay and wire it directly to a switch as per the above post, and go fully manual.

I would imagine the DSPO figured with the Crossfire gone, he didn't need to ECU at all anymore and just cut the connectors off.

at this point, I'd be more than happy to pawn the car off on someone else and get back into a C5... but it keeps me busy, the body is in great shape, and it does run really well, and the "repairs" have yet to cost me a dime.

 

Ok, I will draw a diagram and take a pic of it and then post it here. Give me a few minutes.





I hope you can see it. I had a heck of a time trying to keep shadows away.

 

What I tried was by far simpler, but didn't work.
I just went right from the single blade on the OD unit to a switch which was also connected to the battery.
I got into 2nd, flipped the switch, and nothing.

I did that because I have no idea where the first gear switch is. I looked on the side of the transmission, but I only found a bunch of 2-prong connectors.


what are the two relays you used?

 

The first relay on the left is the arm relay. It is there to keep you from leaving the overdrive on and running the battery dead when you park the car. It's second function is to keep a lot of added current from going through the ignition switch. The coil of the relay uses about 1/10 of an amp, so there is no added load on the ignition switch.
The right relay is the control relay. It takes the current spikes, and may one day fail. The arm relay disconnects it from any circuit when off. The pressure switch in the trans. protects you from a dead battery by turning off with the car sitting still.
To keep the overdrive off if there is an electric fault or a shorted pressure switch, just always leave the car parked in first gear.
I forgot to draw in a fuse. you can always disarm the trans by pulling the fuse, and the arm relay will deactivate, restoring the car to funcionality. Put a fuse in the arm coil wire, and one in the control relay battery power in wire.

The first gear switch is the rear one on the main case shifting fork arm black side cover. Don't confuse it with the back one which is reverse. It might not have a switch on the reverse arm anyway. But I'm not familiar with an '84 case, so the back up light switch might be back there.
To be sure, just put your ohm meter on the switch you think it is, and put it in first. The meter should show max ohms, or not move. When you go back to neutral or any other gear, the switch should show zero ohms, or full meter deflection.

The relays are the little cheap black 30 amp relays that autozone sells for about $4.00.

the relays are a permanent installation. What you did should have gotten it to work. you can get your simple sytem to help you troubleshoot.
Get it back into first gear and instead of putting any battery power to it, use an ohm meter.
Ok,
first, hook the ohm meter to the wire that you put on the overdrive, and the black meter lead to ground.
Then go to ohms X 100 or something close. the meter should read no ohms. Then get the car up to about 15 mph or so in first. The internal pump will be putting out some pressure. It should be enough pressure to activate the pressure switch inside the trans, and it will turn on, connecting your meter to the solenoid, and you should get maybe 15-30 ohms on the meter. When the car stops, or gets down around 5 mph, the meter should go dead again.
What that tells you is :
1. pump is pumping.
2. fluid level is sufficient to feed pump
3. screen inside is relatively clean
4. the meter change signifies that the pressure switch is working
5. the solenoid is not shorted
6. the solenoid ground wire is connected

If you have anything near zero ohms just hooking up the meter, the pressure switch is stuck on, and the solenoid might be shorted. Both of them are easy to change. Don't know where to get them, but they are easy to replace.

If it is switching, the overdrive unit needs repair. the pressure inside the O.D. is bleeding off, bypassing the seals or the clutches are so worn that there is not any thickness to "bite" on the clutchpack, but probably both.

If your speedometer is working, jack up the rear end of the car and do what you did with the switch and battery power. If the clutches and seals are worn, it will have enough pressure to shift and the speedo will jump up as if you shifted gears, but not enough pressure or clutches to push the car.

Good luck on finding a cheap fix.
If you end up finding a good used overdrive, I am interested in the old overdrive case.

Also, just as a side note, there is a sprague clutch inside the O.D. It will engage the in put shaft to the output shaft which is why your trans is still pushing the car. If reverse doesn't work, there is crap in the sprague. or it's destroyed.
The first gear switch is there to keep you from accidentally starting from a stop in overdrive. you can fry the clutches in 10 seconds.

 

 

as much fun as all that sounds, now I have to figure out why my car won't run anymore.

http://forums.corvetteforum.com/c4-g...-is-light.html

when you say "meter should go dead" do you mean read a short?

 

What color wires feed the switch?
I am looking in the right place... it will be a round 2-pin connector?

 

My terminology was incorrect. I said that you should have no ohms. I meant to say you should have "infinity", or max ohms.
I can see why you were confused. sorry 'bout that.

Well, I am not sure on the wire color. I don't have an 84 diagram. Mine's an 86, and in 1986, there is just one switch. It is on the 1-2 arm. I can look at my diagram, and the info I will provide is out of the 86 book.
The book is at my work, and I will add to this post when I get there and remember I was going to do that.
The switch should be a 2 pin switch, with the plastic pin holder in an oval shape with a locking tang.
"Meter go dead" means the ohm meter will look like it does with both wires in free air......max ohms, "infinity"
In other words, the meter will have no reading, then you will have about 30 ohms or so, then when you come to a stop, there will be no reading because the pressure switch opened back up.

Ok, I have the book 101 projects for your corvette. I see your buncha switches problem. The first gear switch is the last one on the shifter cover.
The first one is 4th gear switch, then 2nd gear switch, and the last, rearward is the first gear.......still don't have wire color.

This book says the second gear switch is engaged no matter what gear you are in, and the overdrive won't work without it if you want the ECM to control your overdrive. Check the middle switch with an ohm meter and determine it is any good. Apparently the earlier ECM programming required a trans input to the computer to tell it what gear you are in to have the computer engage or disengage the overdrive based on your vehicle speed and throttle position.

But wait, you are going to make it totally manual, so that is not important. If you use the first gear switch, and you should, just make sure that one is good. If it isn't, you can probably use the 4th gear switch installed in the 1st gear position if it operates the same. (I would guess pushing the switch opens it, and relaxed closes it)

By the way, any distributor that has a vacum cannister hanging off the side is totally mechanical, and has no computer attached to it. Check to see if you have a 4 pin module in it, and if it does, it is a "stand alone" type device. a computer controlled distributor has 7 pins on the module.
By the way, nice job on the wiring diagram.
C-ya