OD light

[kassim503]

I just recently noticed that the overdrive light on the switch seems to be turning on when im stopped and idling, it goes away once i step on the gas, dont matter if im tapping or hammer down, also it dosent seem to be effected by gear chages, Park, N,D but i have not tried the lockouts yet. The light dosent turn on brightly, it kinda flickers like a bad signal. It wont turn off if i turn the switch to off and on or any combination of it. The transmission seems to be shifting fine and with normal points of shift. Is there a vacuum line thats going over to the transmission that could be cracked or disconnected, creating this confusion.

[asavage]

Is there a vacuum line thats going over to the transmission that could be cracked or disconnected, creating this confusion.

I don't think so.

Ignore the coloring:


According to this, unless you have a harness that has rubbed through the insulation and is shorting to ground as the engine moves at idle (not a good ground, but enough to begin to light the lamp), pretty much the only thing that can cause that is a faulty OD Indicator Switch, or some malfunction inside the trans that is causing OD pressure to build when you're stopped.

[kassim503]

oh no I knew the car couldnt let me off easy, it rarely lets me go off scot free.

If the OD clutch was pressurized when the car is idle id notice a slower let off the brake roll right? Due to the clutches rubbing on eachother making me roll slower or even not roll at all? I never really understood the main parts of a transmission, so im defnintiley not experienced on this

Anybody know where the switch is located and how its actuated? I guess its time to start tracing back wire to the source.

[asavage]

I don't have an '83 FSM here right now, but I'm fairly certain it's the single-wire gizmo right behind the OD unit (which is behind the bellhousing):



Easy thing to do is to unplug it from the harness, and see if there's a change. it's only there for the indicator, so you can unplug it with no harm. If the light stays out, either the switch is bad, or something inside.

[kassim503]

I have noticed in the 4th gear during lockup, if i ease off the gas and then kinda step on it moderatley, i notice mabye a 50 rpm change in the tachometer, im not sure if the lockup means 100% and I know factory tachs are not accurate, but its showing a rpm change if i hold my speed and do this. Unless this is caused by the play in the differential and mabye the rear end squatting down a little.. or i could be acclerating, but i never remembered it doing this, but i have also never decided to watch the tach like a hawk.

Would 50 rpms of loss would conclude that there is slippage?

[asavage]

Maybe. You'll know for certain when it becomes 100 RPM difference.

[davehoos]

some lockups refer to 80% slipage being ok.
i think this refers to the slipage that was there normally.

this has a name that i cant remember-at a point most convertors obtain a 1 to 1 tourque transfer/multiplication.

the lockup is a single side clutch with the pressure in the convetor pushing the plate againt the housing.

[asavage]

I just recently noticed that the overdrive light on the switch seems to be turning on when I'm stopped and idling, it goes away once i step on the gas . . .

Reading the note at the top of the page:




"O.D. indicator lamp glows when ignition switch is ON (and engine not running) as well as when it is running in O.D. position."

I can't find a tie-in with the Bulb Check Relay system. This implies that the OD Indicator Switch is NC (normally closed) and opens with pressure. I can't find any info in the FSM to corroborate that, but that is what I'm guessing.

Taking that supposition and running with it: your line pressure may be dropping, due to worn parts and/or internal leakage, and that's causing the OD Indicator Switch to close at idle. Maybe.

[kassim503]

who knows, I think it is a short in wiring by the way the light flickers and how my transmission seems to have ok pressure, shifts arent that plush and there seems to be no detectable slipping. Someday ill check tranny pressure by hooking up a gauge to the npt boss, but thats for a future date.

Now it seems to be on most of the time unless i punch it, it kinda starts flickering. Im guessing torn wiring, and I have a poor guess as to where it is it might be how i reinstalled the center console, i think i squeezed one of the wires and might of pinched it in a screw. Ill pull the little lid under the parking brake and start tugging on the od harness a bit and follow it

[asavage]

The wire you are looking for can't be pinched: it has to move, in order to give that symptom.

[kassim503]

ah thats true, if it was pinched it either be on or off. Well now its on 24/7 and punching the tunnel and center console didnt work, I gotta find out where the wire runs thru, I think it drops down thru the tunnel instead of runs all the way to the firewall

[asavage]

Well now its on 24/7

Probably a bad Indicator Switch then. Unplug it at the trans, it'll go out I bet.

Another couple of views to add to the one above:



OD Indicator Switch is 31041-X8600 -> 31041-X7000, $60

[asavage]

Looking at the hydraulic schematic, I think I'm correct when I guess that the switch is NC and is opened via OD band release pressure. And according the the chart, OD band release pressure is applied in every selector mode except when it's actually in OD.

If the trans seems to shift OK, I put my money on a faulty switch.

[kassim503]

ah, your prolly right, personally, i dont care, in fact i care so little about the light being on that if its not a sign of the tranny losing pressure or anything mechanical i dont care. Ill try disconnecting it, if it puts the light out ill reconnect it and thatll be it. I cant even see the light during the day, and it helps me stay up at night so whatever, probably not gonna make an effort to replace it, its more labor and money than i wanna spend. (60 bucks can buy alot of things)

The tranny is shifting just fine, so im not suspecting line pressure loss and other things, im pretty sure its the switch because in all my years of owning cars I have never seen a frayed wire. (except for mouse damage) and this car has not sat for longer than a week in its life.

[davehoos]

the overdrive indicator light switch is normally closed switch.

line pressure in the overdrive cancel circuit opens the contact in in the switch.if the engine is not running there is no oil pressure so the light come on,also it will flicker when you run low on oil.

the system is different on later models.its operated off the control box.