I have a 1985 240 Wagon with 260/k miles on it. When I am driving for long distances in 5th gear (push button type), all of a sudden the car starts going 5th to 4th gear (very quickly). Usually if I shut the car off and then get going again, it is ok for a while. My mechanic thought it might be the overdrive cellinoide sping (worn out)? I was thinking that it might be the overdrive relay switch in the glove box. Has anyone had similar experiences?

Since the OD goes in and out on its own several times, the dash light is on during all these occurences. This indicates the relay is OK. Trouble is elsewhere. If power dropped because of the relay, the OD would not re-engage on its own. Loss of power or ground refernece to a latched relay disrupts the latching circuit which must be re-energized to relatch. Something the circuit does not do on its own. Leave the relay alone.

First and foremost. Fluid level OK??

While you are checking the fluid level:

With ignition ON, Engine OFF, gear in 4th and OD dash light ON. Wiggle the wires at the solenoid. Dirty corroded, loose contacts love to cause this symptom as well as broken wires inside the insulation right at the crimp point. Any clicking of the solenoid points to the area of the wire you are fiddling with at that time. Work your way up the yellow wire to eliminate any hidden wire breaks.

If not able to click the solenoid, is 12 volts getting to the solenoid? Check yellow feed wire. If 12 volts at solenoid yellow feed wire, reconnect to the solenoid, take off the ground terminal and check for voltage between the ground terminal and some other ground. No voltage solenoid is shot. Replace. This is best done after the symptoms have manifested themselves. Gives the solenoid windings time to heat up as if having been driven for a long time.

Duane

Resolder the relay first. $0, 15 minutes, no risk, clean 'n easy job. If it helps nothing, you're out nothing.

They all suffer that symptom sooner or later.
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Don Foster (near Cape Cod, MA)

Relay and fluid level first. After that, the 4th gear switch. If it is the switch you can affect in and out of OD by holding the gear shift lever in various positions to jiggle the switch. Don't even worry until you check these 3 things.

It's the o-ring seals on your overdrive.

You need to have the OD cracked open and have new o-rings put on the pistons.

The reason it occurs on long trips is due to the OD fluid getting hot and thinning out, hence making it's way past the worn o-rings, decreasing the overall pressure, and giving you your loss of overdrive.

Not neccesarily. My 245 was doing the exact same thing on a long trip. I was having all sorts of bad thoughts about O-rings as I drove down the road in 4th gear. Looked under there when we stopped for gas and the wire had come loose from the solenoid and the wind was blowing it on and off the connector. Moral: check simple things first.
--
Bob W.
16 Volvos ('58-'91)
445-544-122-240-740
Four turbos