Ray03

A little background on the car. I bought it a year ago as a running fixer-upper. Has 129K miles. Everything has been working as it should until a few days ago when the OD seemed to not want to disengage. From what I've read it looks as if the previous owner did the mod which made it to where I could engage the OD whenever I wanted. By pressing the button on the shifter I could engage and disengage the OD at will. Now, when I take off in first gear, it runs and revs as it should but as soon as I shift into 2nd, 3rd or 4th, the OD light comes on and it engages. The revs drop as they normally would so I know it's engaging. When I downshift back into first gear, the light turns off and the OD disengages. I've replaced the relay and I've checked the OD fluid level which was fine. I also cleaned and retaped all the wires feeding the relay which were bare. I will check for power at the switch but not sure that would cause this issue. I've also read that there's a solenoid that may be stuck? I'm looking for the electrical diagram but that's proving difficult.

Any ideas on what may be causing this would be greatly appreciated.
Thanks-

s carter

When you click the switch there's no drop out, and you know its dropping out? Or is the light just going out.
You can test if the request for on and off by wrapping a piece of wire to OD feed and connect a DMM or Test light plug the feeder back in and go for a ride then you see what request is sent to the trans and rule out or condemn said solenoid and other things inside the transmission (know if its inside or outside the transmission)

IHBD

In the 85, the actual switch on the shifter is at the base of the shifter shaft, joined by two small wires. If one of these wires breaks, Overdrive is commanded at all times, and Overdrive will engage anytime the transmission is not in 1st. This sounds like your symptoms. Lift the console top cover and take a look at the wires. If one is broken, that's your issue. Broken wire happened to my 85 many years ago.

Ray03

Thanks for the replies. I will check the wires on the switch and hopefully it's as simple as that.

IHBD - to answer your question, no, I could never command overdrive in first with the button. It was always only available in 2nd through 4th gears.

s carter - the light comes on in 2nd through 4th gears due to the OD being on. The light goes off when I downshift into 1st gear. Normally, I'd have to press the button to engage OD and get the light to turn on.

I'll report back after I pull the console and check the switch wires.

Thanks-

2011KLR

Isnt the name 4+3 derrived from the fact that the OD disengages in first gear? Otherwise it' be a 4+4.

Or, maybe i just dont understand the actual problem. If so, i will watch from the sidelines.

weeles

The standard setting for the 4+3 on start up is always active and will perform as you are describing, at least that is what my 86 does with the button on the shifter. Although I realize that the 85 had the switch on the centre consul and this has been changed to the shifter button, maybe the PO has made the conversion to operate like the later design as well.
When you are driving and in an overdriven gear and accelerate hard , does the OD disengage as its supposed to?
I think what you are trying to express is that if you are driving in overdrive and hit the button the OD does not disengage?

VikingTrad3r

in to see the solution. 👍

Ray03

Thanks for all of the input, I really appreciate it. I'm going to start by checking the switch wires as this seems to be the simplest next step. I'll pull the center console and see what's going on with that.

Just to be clear for those following this thread;
1. The OD button is on the shifter in my car
2. Originally, the only way for me to engage the OD was to press the button. I could choose to have it on or off as I wanted (2nd through 4th gear). When OD was engaged, the OD light came on.
3. First gear never had the OD option and still doesn't.
4. Now the car pulls as it should in 1st with the RPM's accordingly.
5. As soon as I shift into 2nd, the OD engages, light comes on and RPM's drop accordingly.
6. Pressing the button doesn't disengage the OD or the light.
7. Downshifting into 1st automatically disengages OD
8. I'm basically stuck in OD other than in 1st gear.

After doing a bit of research, I'm still confused as to how the OD was originally intended to work. Unless I've misunderstood, it seems that the ECM would automatically engage the OD when the car was at certain RPM's in 2nd-4th gears. The button was to turn it off if so desired. So the previous owner altered it somehow to make it a fully manual system by over-riding the ECM? I'm just trying to figure out how it's supposed to work so I have a better idea of what to look for if it's not just a broken wire.

Thanks again!

IHBD

The PO probably hasn't done anything to change the OD control system. I suspect that you have a stock configuration later 85 with the OD control mounted in the shifter with a broken wire that prevents commanding the OD off. Fix the wires and enjoy your car.

jdjenk

I also had problems breaking wires, eventually I just made it longer and I haven't had a problem since.

LiveWire1

On my 85, I happened to break the input shaft of the 1-2 shifter arm going into the transmission, all because I was showing off with a snappy power shift. I ended up driving 350 miles home using only third, fourth and OD. It took me weeks of looking to find a shifter arm from a Super T-10 from the 70's on eBay, as an 85 arm was nowhere to be found. On the original 85 shaft, there is a flat spot which corresponds to the switch on the shifter cover on the transmission that disables the OD in first gear. There's so much torque there that it would ruin the OD if applied in first. The 70's arm didn't have that flat spot, and I wasn't about to start grinding a new one. Also, the flats at the end of the shaft didn't match the angle of the 85 shifter arm, so I had to make a new arm out of 1/4" stock (Which took me 5 tries before I got it right. It has to be snug with ZERO play at all.) Rather than risk taking off from a stop inadvertently in 1st OD, I took a 12 volt proximity sensor and mounted it under the console, where it would sense the shifter in 4th gear, and energize a 12 volt relay to close the contacts on the two wires that used to sense the flat spot on the arm. This gave me overdrive in 4th gear. I really don't see the need to have OD in 2nd or 3rd, so I'm happy with this setup. Also, I have the console switch for OD, so it works well for me. BTW, don't power shift your 4 speed. The shifter is garbage, and it doesn't have the stops like a good Hurst shifter, to prevent bending shifter arms or snapping shafts. I wish a decent shifter for the 4+3 was available, but I guess I'll have to make do with the stock one.

Ray03

Thank you for everyone who responded to my questions. I pulled the center console as advised and it did turn out to be a broken wire. It had completely snapped. I fixed them both because the other wire was about to also break off. I ended up extending them a few inches to give myself a bit more slack. They were both incredibly tight and short Reassembled everything this weekend and all is working as it should.

Thanks again for all the help!