You have no relay in the 80. It is all direct wire with two switches in the system.

Dash light is the key to what part of the wiring the problem lies.

If the dash light stayed on, look at the wiring under the auto, the 4th gear switch on the tranny, and the terminals at the solenoid.

If the dash light went off, look at the shifter switch and the wires to it. Th ewires tend to break at the flex point where they enter the shifter from the right.

Duane

...also check and clean the spade connecters at the solenoid that screws into the OD body.

Bet you anything it's the switch.

I was experiencing the same thing on my '80 last week. As stated below, there is no relay for our sliding switch style OD.

In my case, slapping the top of the shifter knocked it back into OD. I took the switch out, sprayed some electrical contact stuff in it, and it's been working perfect ever since... It even slides nicer too.
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If you listen to the radio in Portland, OR, you may know me as 'Portland's Favorite Soul Brother!'

No, the 1980 and older 240s did not have an O/D relay. 1981 and newer ones with the momentary push button switch on the gearshift did have an o/d relay but the older ones with the slider on/off switches did not. You're problem is likely to do with the wiring or perhaps the switch is worn out.

Good luck with it,

Roj