I am having problems with the overdrive on my 1987 240 wagon with automatic transmission. About a month ago the car quit going into 4th gear (OD), as though the lockout button had been engaged on the shift lever. The light on the dash would come on and off as the switch was operated, but it would have no effect on the OD. I removed the solenoid and checked it by applying 12 volts directly to the solenoid, and it did not operate, so I assumed that was the problem and bought a new one.

While installing the new solenoid I decided to check the voltage from the wire to the solenoid to see if the switch and relay were working. I initially found that I had 12 volts on the wire all the time, no matter the position of the switch. Also the light on the dash had quit coming on when the switch was operated. The relay was still clicking, but I decided to crack it open and see what was going on inside. I found a bad solder joint on the back and re-soldered it. After I did this I would get 12 volts at the wire only when the switch was off, and the dash light would come on when the switch was on. I put it all back together and everything appeared to be working great (dash light on when supposed to be, solenoid clicks when switch operated).

I road tested it that night and everything was working fine. The next morning it was back to no OD. After about 15 minutes on the road it eventually goes into OD. The light on the dash still comes on with the switch, and after it goes into OD the switch will kick it back out when engaged.

I am out of ideas, and am planning on doing the dremel surgery to my old solenoid to remove the circuit from the equation. Does anyone have any other ideas of things I could check?

Thanks

I, too, have had OD problems recently (arrow turns on and off, solenoid makes proper clicking noise, but intermittent drop from 4th to 3rd gear.) I looked around for all the common suspects but found nothing obvious. I am not familiar with checking for electrical problems so I did the best I could without using a meter of any kind. In the end I did 2 things and have not had any trouble since:flushed the transmission and did the Dremel modification to the solenoid. I was comfortable doing this because I figured it might save me much more OD grief in the future and because I don't recall ever having used the OD button to lockout 4th gear and don't anticipate needing it in the future. My transmission is now a nicely functioning full-time 4-gear tranny that gives me no trouble. Neither the flush nor the solenoid modification were very involved or time comsuming. By the way, my mechanic had recommended a ($1400) transmission rebuild. My total cost came to less than $50. Good luck.
-Chris

PS- here is a link to the IPD flush instructions they provide with their special hose. http://www.ipdusa.com/pdf/PI-241attrannyflush.pdf (but you don't need their hose to do the flush)

Thanks to the good people in this forum I just solved the EXACTLY same problem with my 940 Turbo AW-71 tranny. The mechanic checked all the cabling, o/d relay and solenoid. He never found a problem with the cabling. He wanted to do a full overhaul to the tranny but THANKS to the guys here, I solved the problem myself with a flush, it was less than 35 bucks and saved me a week at the tranny shop plus several hundred bucks................

GO FOR A FLUSH FIRST!!!! .......... wait a couple days and the O/D should be back in place. These trannies are bullet proof.

940 Turbo 16" Dunlops, comp exhaust, bilsteins, 64kmiles.

I just did a full trans flush for a different reason, but discovered that it is really easy to do. I would recomend doing it anyway if you never have. There is good directions in the FAQ's. All you really need to get to do it is the right size of clear tubing for a couple bucks and your set. If you are going to switch to synthetic, first flush it out with the cheapest atf you can find. Good luck.

From your description of symptoms, it sounds like the bad solenoid was the cause for the melted contact in the relay. The problem that you're having now is possibly internal to the transmission. Since the OD operates after the transmission is warmed up, the problem can be caused by sludge in the transmission. You may want to do a transmission flush and see if it helps. Just a opinion.
steve

I concur, give it a flush if you are sure the solonoid is engaging correctly. You should hear and feel the solonoid click, with key on (no need to start engine), while someone toggles the switch.

I solved a simlilar problem with a flush using symthetic ATF.
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David Hunter

You have the controls pretty well figured out, but a minor point is the switch. It's not an ON-OFF type, but a momentary contact push-button. Whenever it's pushed, it should "toggle" the relay to it's opposite state.

If you like the switch-controlled downshift, as I do, the control circuit is really pretty simple. It involves 5 components and the wiring that connects them. (Flushing is a good idea too.)

1) Fuse 11 (200) or 12 (700/900) supplies voltage to items #2, #3, #4, and #5
2) The Shifter button/switch (turns OD relay off and on)
3) The OD relay (controls Upshift Arrow light and Solenoid - separate wires)
4) The Upshift Arrow light (ON means relay and OD are OFF)
5) The OD solenoid (Allows OD engagement when ON, the "default" Relay state at Key On)

If the Shifter switch makes the Arrow light (#4) go on and off, then items 1, 2, and 3 are probably OK, and the problem is most likely the undercar wire to the Solenoid (#5) or the wire connector terminal.

Less likely would be be Solenoid itself.
Also possible (but less likely) would be the relay controlling the Arrow light (#4) correctly, but failing to activate the Solenoid.
An internal transmission problem is also possible.

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Sorry for the mix-up, David. My comment was meant to address Sweedforspeeds's original post and his understanding of how things worked. I should have posted under his post.

I agree that the OD Relay application is tricky (but effective). The "output" (T-87, 87a) actually comes from what is normally the armature input on a typical relay.

So, depending on the relay's state, T-87 (to solenoid) and T-87a (to bulb) are in contact with either T-15 (+12V) or T-31 (ground).

And since T-15 gets direct +12V at Key On, the relay is initially set "ON" to the Solenoid ON—Arrow OFF state, where it stays until/unless the shifter switch diverts +12V from T-15 to T-86 to toggle the relay "OFF".

I'm sure you know all this, but it might help some other reader.

Bruce
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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.

Yes I know it's not really a toggle switch but I used that word because it toggles the solonoid and light off and on. Actually post 85 or so there is only 1 contact on the rely used for both the light and solonoid.
As I analyze the circuit it works like this:

12 volts is supplied to bulb, other side of bulb goes to relay contact, then to solonoid, when solonoid is open, bulb lights as it gets a ground through the solonoid coil.

When solonoid picks 12 volts flows to solonoid and it too picks but now there is 12V both sides of the bulb so it goes out.

This circuit is often misunderstood by Bricksters, earlier models used the NO and NC contacts on the relay to do the same thing.

It really is amazing what a flush can do for the durable AW70 trannies especially if you go to over to synthetic, that has been my experience. I have cured 2 tranny problems (hard shifting and no OD) on my old 740 and my daughters 240.
Flushed my current V90 well as a preventive measure.

David Hunter

David,

See this AM's post above -- seems I wasn't awake enough to put it where I wanted it, at this point in the thread.

Bruce

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Bruce Young
'93 940-NA (current) — 240s (one V8) — 140s — 122s — since '63.