hi-
i just purchased an 83 240 with the m46 4-speed with electronic overdrive. the previous owner was a volvo guy who knew quite a bit about the car and told me that in cold weather the electronic OD sometimes would not engage, and that it was best to put in the clutch before pushing the button to go into overdrive. i'm looking to solve this problem completely. any suggestions? thanks!

In the 83 if the dash light is on, your 4th gear switch on thetransmission is working OK.

OD working when cold but not hot is actuating piston O-ring seals.

Now that it is not working at all, it still is the O-rings, they finally failed big time.

See: http://www.brickboard.com/FAQ/700-900/OverdriveRebuild.htm

for what needs to be done.

Duane

I've been holding off rebuilding the overdrive on my 83 because I thought the Pressure Release Valve tool was going to be a must. I'm no good at drilling with no drill at the moment. Rereading the FAQ section I realize now that its not totally needed to do the job.

Rebuild seems pretty straight forward now. Be putting the rebuild kit to use now. Thanks Duane for all the info available to do so. Although I am curious to know if Redline ATF would actually help prolong the need.

I'd try changing the transmission fluid. Redline MTL comes recommended for smooth shifting.
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1980 245 Canadian B21A with SU carb but electronic ignition and M46 trans in Brampton, Ont.

If its temperature related as to needing to be warmed up I'd be almost certain that its the 4th gear overdrive switch.

Its a simple job but you need an 02 sensor socket I believe or that is the size the switch requires to torque it. The sensor sits on the passenger side of the transmission on the top. If its not engaging then pull the stick shifter towards the passenger seat and to the rear as you engage it. This will sometimes help it. The transmission heats up and expands enough for the switch to make contact so by pulling the stick shifter your going to do essentially the same thing. Although sometimes its a combination of it warming up just a little and pulling.

i tried your advice without success. after driving it for a while, i haven't had any success in getting the OD to work at all. i should note that the green OD light comes on in the dash, so i'm guessing that the relay and button on the shifter are in working order, and that it is indeed the switch on the transmission. can anyone confirm?
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87 244, 235K (sold) and 87 245, 314K (RIP), 95 850 GLT 201K and ever climbing

With the ignition on, put the car into 4th gear and while stretching to push the button hold your head out the door to listen for the solenoid to click. Nice click means the wiring is working to the Solenoid.

My 83 when bought had a non working OD on the M46. I emptied the fluid and cleaned two screens. When you take off the bottom plate on the OD there will be a rectangular screen that pops off. I used throttle body cleaner to spray it out. Not sure what the best stuff to use would be. Then there are three circles with two little dimples that allow for opening. The one on the passenger side is the only one you want to open. Inside is a round tubular screen that I cleaned. Refilled with Type F auto transmission fluid (Redline best) and after a couple weeks I had the urge to try the OD on the freeway. It worked but its been working occasional when not too hot.

My next plan is to swap out the solenoid and possibly rebuild or replace with another lower milage OD unit/M46 I can obtain cheap. Although since I have a 10 hour trip (roundtrip) planned in two weeks I'm looking to just fill it with Redline rather than the stuff I have in it at the moment in hopes it will help.

I would listen for a click, if that works then go with cleaning the two screens and refilling with Redline Type F synthetic. I found a tool at Harbor Freight for $6 that will open the round filter cover.